--- a/NEWS	Mon Apr 03 18:09:04 2023 +0200
+++ b/NEWS	Mon Apr 03 20:53:14 2023 +0200
@@ -1,11 +1,19 @@
 Pending changes in the mainline
 ===============================
 
+General
+-------
+
+* Support for labels associated with patients, studies, series, and instances
+
 REST API
 --------
 
 * API version upgraded to 20
-* /system: added "UserMetadata"
+* New URIs "/.../{id}/labels/{label}" to test/set/remove labels
+* The "/patients/{id}", "/studies/{id}", "/series/{id}" and "/instances/{id}"
+  contain the "Labels" field
+* "/system": added "UserMetadata"
 
 Plugins
 -------
@@ -18,7 +26,7 @@
 
 * Enforce the existence of the patient/study/instance while creating its archive
 * Security: New configuration option "RestApiWriteToFileSystemEnabled"
-  to allow "/instances/../export" that is now disabled by default
+  to allow "/instances/../export" (the latter is now disabled by default)
 * Fix issue 214: VOILUTSequence is not returned in Wado-RS
 * Fix /tools/reset crashing when ExtraMainDicomTags were defined
 
@@ -34,7 +42,7 @@
   AcceptedTransferSyntaxes.
 * Made the default SQLite DB more robust wrt future updates like
   adding new columns in DB.
-* Made the HTTP Client errors more verbose by including the url in the logs.
+* Made the HTTP Client errors more verbose by including the URL in the logs.
 * Optimization: now using multiple threads to transcode files for
   asynchronous download of studies archive.
 * New configuration "KeepAliveTimeout" with a default value of 1 second.
@@ -145,7 +153,7 @@
 * Housekeeper plugin: Fix resume of previous processing
 * Added missing MOVEPatientRootQueryRetrieveInformationModel in 
   DicomControlUserConnection::SetupPresentationContexts()
-* Improved HttpClient error logging (add method + url)
+* Improved HttpClient error logging (add method + URL)
 
 REST API
 --------

--- a/OrthancServer/CMakeLists.txt	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/CMakeLists.txt	Mon Apr 03 20:53:14 2023 +0200
@@ -228,16 +228,15 @@
 #####################################################################
 
 set(ORTHANC_EMBEDDED_FILES
-  CONFIGURATION_SAMPLE         ${CMAKE_SOURCE_DIR}/Resources/Configuration.json
-  DICOM_CONFORMANCE_STATEMENT  ${CMAKE_SOURCE_DIR}/Resources/DicomConformanceStatement.txt
-  FONT_UBUNTU_MONO_BOLD_16     ${CMAKE_SOURCE_DIR}/Resources/Fonts/UbuntuMonoBold-16.json
-  LUA_TOOLBOX                  ${CMAKE_SOURCE_DIR}/Resources/Toolbox.lua
-  PREPARE_DATABASE             ${CMAKE_SOURCE_DIR}/Sources/Database/PrepareDatabase.sql
-  UPGRADE_DATABASE_3_TO_4      ${CMAKE_SOURCE_DIR}/Sources/Database/Upgrade3To4.sql
-  UPGRADE_DATABASE_4_TO_5      ${CMAKE_SOURCE_DIR}/Sources/Database/Upgrade4To5.sql
-
-  INSTALL_TRACK_ATTACHMENTS_SIZE
-  ${CMAKE_SOURCE_DIR}/Sources/Database/InstallTrackAttachmentsSize.sql
+  CONFIGURATION_SAMPLE            ${CMAKE_SOURCE_DIR}/Resources/Configuration.json
+  DICOM_CONFORMANCE_STATEMENT     ${CMAKE_SOURCE_DIR}/Resources/DicomConformanceStatement.txt
+  FONT_UBUNTU_MONO_BOLD_16        ${CMAKE_SOURCE_DIR}/Resources/Fonts/UbuntuMonoBold-16.json
+  LUA_TOOLBOX                     ${CMAKE_SOURCE_DIR}/Resources/Toolbox.lua
+  PREPARE_DATABASE                ${CMAKE_SOURCE_DIR}/Sources/Database/PrepareDatabase.sql
+  UPGRADE_DATABASE_3_TO_4         ${CMAKE_SOURCE_DIR}/Sources/Database/Upgrade3To4.sql
+  UPGRADE_DATABASE_4_TO_5         ${CMAKE_SOURCE_DIR}/Sources/Database/Upgrade4To5.sql
+  INSTALL_TRACK_ATTACHMENTS_SIZE  ${CMAKE_SOURCE_DIR}/Sources/Database/InstallTrackAttachmentsSize.sql
+  INSTALL_LABELS_TABLE            ${CMAKE_SOURCE_DIR}/Sources/Database/InstallLabelsTable.sql
   )
 
 if (STANDALONE_BUILD)

--- a/OrthancServer/Plugins/Engine/OrthancPluginDatabase.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Plugins/Engine/OrthancPluginDatabase.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -1437,8 +1437,8 @@
     }
 
 
-    virtual void GetLabels(std::set<std::string>& target,
-                           int64_t resource) ORTHANC_OVERRIDE
+    virtual void ListLabels(std::set<std::string>& target,
+                            int64_t resource) ORTHANC_OVERRIDE
     {
       throw OrthancException(ErrorCode_InternalError);  // Not supported
     }

--- a/OrthancServer/Plugins/Engine/OrthancPluginDatabaseV3.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Plugins/Engine/OrthancPluginDatabaseV3.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -1051,8 +1051,8 @@
     }
 
 
-    virtual void GetLabels(std::set<std::string>& target,
-                           int64_t resource) ORTHANC_OVERRIDE
+    virtual void ListLabels(std::set<std::string>& target,
+                            int64_t resource) ORTHANC_OVERRIDE
     {
       throw OrthancException(ErrorCode_InternalError);  // Not supported
     }

--- a/OrthancServer/Plugins/Engine/OrthancPluginDatabaseV4.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Plugins/Engine/OrthancPluginDatabaseV4.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -1163,8 +1163,8 @@
     }
 
 
-    virtual void GetLabels(std::set<std::string>& target,
-                           int64_t resource) ORTHANC_OVERRIDE
+    virtual void ListLabels(std::set<std::string>& target,
+                            int64_t resource) ORTHANC_OVERRIDE
     {
       throw OrthancException(ErrorCode_NotImplemented);
     }

--- a/OrthancServer/Sources/Database/IDatabaseWrapper.h	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/Database/IDatabaseWrapper.h	Mon Apr 03 20:53:14 2023 +0200
@@ -250,8 +250,8 @@
       virtual void RemoveLabel(int64_t resource,
                                const std::string& label) = 0;
 
-      virtual void GetLabels(std::set<std::string>& target,
-                             int64_t resource) = 0;
+      virtual void ListLabels(std::set<std::string>& target,
+                              int64_t resource) = 0;
     };
 
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/OrthancServer/Sources/Database/InstallLabelsTable.sql	Mon Apr 03 20:53:14 2023 +0200
@@ -0,0 +1,24 @@
+-- Orthanc - A Lightweight, RESTful DICOM Store
+-- Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+-- Department, University Hospital of Liege, Belgium
+-- Copyright (C) 2017-2023 Osimis S.A., Belgium
+-- Copyright (C) 2021-2023 Sebastien Jodogne, ICTEAM UCLouvain, Belgium
+--
+-- This program is free software: you can redistribute it and/or
+-- modify it under the terms of the GNU General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful, but
+-- WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+-- General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License
+-- along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+CREATE TABLE Labels(
+       internalId INTEGER REFERENCES Resources(internalId) ON DELETE CASCADE,
+       label TEXT
+       );

--- a/OrthancServer/Sources/Database/PrepareDatabase.sql	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/Database/PrepareDatabase.sql	Mon Apr 03 20:53:14 2023 +0200
@@ -91,6 +91,12 @@
        patientId INTEGER REFERENCES Resources(internalId) ON DELETE CASCADE
        );
 
+-- New in Orthanc 1.12.0
+CREATE TABLE Labels(
+       internalId INTEGER REFERENCES Resources(internalId) ON DELETE CASCADE,
+       label TEXT
+       );
+
 CREATE INDEX ChildrenIndex ON Resources(parentId);
 CREATE INDEX PublicIndex ON Resources(publicId);
 CREATE INDEX ResourceTypeIndex ON Resources(resourceType);

--- a/OrthancServer/Sources/Database/SQLiteDatabaseWrapper.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/Database/SQLiteDatabaseWrapper.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -1084,21 +1084,50 @@
     virtual void AddLabel(int64_t resource,
                           const std::string& label) ORTHANC_OVERRIDE
     {
-      throw OrthancException(ErrorCode_NotImplemented);
+      if (label.empty())
+      {
+        throw OrthancException(ErrorCode_ParameterOutOfRange);
+      }
+      else
+      {
+        SQLite::Statement s(db_, SQLITE_FROM_HERE, "INSERT INTO Labels (internalId, label) VALUES(?, ?)");
+        s.BindInt64(0, resource);
+        s.BindString(1, label);
+        s.Run();
+      }
     }
 
 
     virtual void RemoveLabel(int64_t resource,
                              const std::string& label) ORTHANC_OVERRIDE
     {
-      throw OrthancException(ErrorCode_NotImplemented);
+      if (label.empty())
+      {
+        throw OrthancException(ErrorCode_ParameterOutOfRange);
+      }
+      else
+      {
+        SQLite::Statement s(db_, SQLITE_FROM_HERE, "DELETE FROM Labels WHERE internalId=? AND label=?");
+        s.BindInt64(0, resource);
+        s.BindString(1, label);
+        s.Run();
+      }
     }
 
 
-    virtual void GetLabels(std::set<std::string>& target,
-                           int64_t resource) ORTHANC_OVERRIDE
+    virtual void ListLabels(std::set<std::string>& target,
+                            int64_t resource) ORTHANC_OVERRIDE
     {
-      throw OrthancException(ErrorCode_NotImplemented);
+      target.clear();
+
+      SQLite::Statement s(db_, SQLITE_FROM_HERE, 
+                          "SELECT label FROM Labels WHERE internalId=?");
+      s.BindInt64(0, resource);
+
+      while (s.Step())
+      {
+        target.insert(s.ColumnString(0));
+      }
     }
   };
 
@@ -1373,9 +1402,9 @@
                                "Incompatible version of the Orthanc database: " + tmp);
       }
 
-      // New in Orthanc 1.5.1
       if (version_ == 6)
       {
+        // New in Orthanc 1.5.1
         if (!transaction->LookupGlobalProperty(tmp, GlobalProperty_GetTotalSizeIsFast, true /* unused in SQLite */) ||
             tmp != "1")
         {
@@ -1384,6 +1413,15 @@
           ServerResources::GetFileResource(query, ServerResources::INSTALL_TRACK_ATTACHMENTS_SIZE);
           db_.Execute(query);
         }
+
+        // New in Orthanc 1.12.0
+        if (!db_.DoesTableExist("Labels"))
+        {
+          LOG(INFO) << "Installing the \"Labels\" table";
+          std::string query;
+          ServerResources::GetFileResource(query, ServerResources::INSTALL_LABELS_TABLE);
+          db_.Execute(query);
+        }
       }
 
       transaction->Commit(0);

--- a/OrthancServer/Sources/Database/StatelessDatabaseOperations.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/Database/StatelessDatabaseOperations.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -939,6 +939,11 @@
             }
           }
 
+          if (expandFlags & ExpandResourceDbFlags_IncludeLabels)
+          {
+            transaction.ListLabels(target.labels_, internalId);
+          }
+
           std::string tmp;
 
           if (LookupStringMetadata(tmp, target.metadata_, MetadataType_AnonymizedFrom))
@@ -3519,4 +3524,96 @@
     Apply(operations);
     return operations.GetStatus();
   }
+
+
+  void StatelessDatabaseOperations::ListLabels(std::set<std::string>& target,
+                                               const std::string& publicId,
+                                               ResourceType level)
+  {
+    class Operations : public ReadOnlyOperationsT3<std::set<std::string>&, const std::string&, ResourceType>
+    {
+    public:
+      virtual void ApplyTuple(ReadOnlyTransaction& transaction,
+                              const Tuple& tuple) ORTHANC_OVERRIDE
+      {
+        ResourceType type;
+        int64_t id;
+        if (!transaction.LookupResource(id, type, tuple.get<1>()) ||
+            tuple.get<2>() != type)
+        {
+          throw OrthancException(ErrorCode_UnknownResource);
+        }
+        else
+        {
+          transaction.ListLabels(tuple.get<0>(), id);
+        }
+      }
+    };
+
+    Operations operations;
+    operations.Apply(*this, target, publicId, level);
+  }
+
+
+  void StatelessDatabaseOperations::ModifyLabel(const std::string& publicId,
+                                                ResourceType level,
+                                                const std::string& label,
+                                                LabelOperation operation)
+  {
+    class Operations : public IReadWriteOperations
+    {
+    private:
+      const std::string& publicId_;
+      ResourceType       level_;
+      const std::string& label_;
+      LabelOperation     operation_;
+
+    public:
+      Operations(const std::string& publicId,
+                 ResourceType level,
+                 const std::string& label,
+                 LabelOperation operation) :
+        publicId_(publicId),
+        level_(level),
+        label_(label),
+        operation_(operation)
+      {
+      }
+
+      virtual void Apply(ReadWriteTransaction& transaction) ORTHANC_OVERRIDE
+      {
+        ResourceType type;
+        int64_t id;
+        if (!transaction.LookupResource(id, type, publicId_) ||
+            level_ != type)
+        {
+          throw OrthancException(ErrorCode_UnknownResource);
+        }
+        else
+        {
+          switch (operation_)
+          {
+            case LabelOperation_Add:
+              transaction.AddLabel(id, label_);
+              break;
+
+            case LabelOperation_Remove:
+              transaction.RemoveLabel(id, label_);
+              break;
+
+            default:
+              throw OrthancException(ErrorCode_ParameterOutOfRange);
+          }
+        }
+      }
+    };
+
+    if (!Toolbox::IsAsciiString(label))
+    {
+      throw OrthancException(ErrorCode_ParameterOutOfRange, "A label must only contain ASCII characters");
+    }
+    
+    Operations operations(publicId, level, label, operation);
+    Apply(operations);
+  }
 }

--- a/OrthancServer/Sources/Database/StatelessDatabaseOperations.h	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/Database/StatelessDatabaseOperations.h	Mon Apr 03 20:53:14 2023 +0200
@@ -62,6 +62,9 @@
     size_t                              fileSize_;
     std::string                         fileUuid_;
     int                                 indexInSeries_;
+
+    // New in Orthanc 1.12.0
+    std::set<std::string>               labels_;
   };
 
   enum ExpandResourceDbFlags
@@ -70,10 +73,12 @@
     ExpandResourceDbFlags_IncludeMetadata         = (1 << 0),
     ExpandResourceDbFlags_IncludeChildren         = (1 << 1),
     ExpandResourceDbFlags_IncludeMainDicomTags    = (1 << 2),
+    ExpandResourceDbFlags_IncludeLabels           = (1 << 3),
 
     ExpandResourceDbFlags_Default = (ExpandResourceDbFlags_IncludeMetadata |
                                      ExpandResourceDbFlags_IncludeChildren |
-                                     ExpandResourceDbFlags_IncludeMainDicomTags)
+                                     ExpandResourceDbFlags_IncludeMainDicomTags |
+                                     ExpandResourceDbFlags_IncludeLabels)
   };
 
   class StatelessDatabaseOperations : public boost::noncopyable
@@ -82,6 +87,12 @@
     typedef std::list<FileInfo> Attachments;
     typedef std::map<std::pair<ResourceType, MetadataType>, std::string>  MetadataMap;
 
+    enum LabelOperation
+    {
+      LabelOperation_Add,
+      LabelOperation_Remove
+    };
+
     class ITransactionContext : public IDatabaseListener
     {
     public:
@@ -312,6 +323,12 @@
       {
         return transaction_.LookupResourceAndParent(id, type, parentPublicId, publicId);
       }
+
+      void ListLabels(std::set<std::string>& target,
+                      int64_t id)
+      {
+        transaction_.ListLabels(target, id);
+      }
     };
 
 
@@ -424,6 +441,18 @@
                              unsigned int maximumPatients,
                              uint64_t addedInstanceSize,
                              const std::string& newPatientId);
+
+      void AddLabel(int64_t id,
+                    const std::string& label)
+      {
+        transaction_.AddLabel(id, label);
+      }
+
+      void RemoveLabel(int64_t id,
+                    const std::string& label)
+      {
+        transaction_.RemoveLabel(id, label);
+      }
     };
 
 
@@ -687,5 +716,14 @@
                               bool hasOldRevision,
                               int64_t oldRevision,
                               const std::string& oldMd5);
+
+    void ListLabels(std::set<std::string>& target,
+                    const std::string& publicId,
+                    ResourceType level);
+
+    void ModifyLabel(const std::string& publicId,
+                     ResourceType level,
+                     const std::string& label,
+                     LabelOperation operation);
   };
 }

--- a/OrthancServer/Sources/OrthancRestApi/OrthancRestResources.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/OrthancRestApi/OrthancRestResources.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -1971,6 +1971,129 @@
 
 
 
+  // Handling of labels -------------------------------------------------------
+
+  static void ListLabels(RestApiGetCall& call)
+  {
+    if (call.IsDocumentation())
+    {
+      ResourceType t = StringToResourceType(call.GetFullUri()[0].c_str());
+      std::string r = GetResourceTypeText(t, false /* plural */, false /* upper case */);
+      call.GetDocumentation()
+        .SetTag(GetResourceTypeText(t, true /* plural */, true /* upper case */))
+        .SetSummary("List labels (new in Orthanc 1.12.0)")
+        .SetDescription("Get the labels that are associated with the given " + r)
+        .SetUriArgument("id", "Orthanc identifier of the " + r + " of interest")
+        .AddAnswerType(MimeType_Json, "JSON array containing the names of the labels")
+        .SetHttpGetSample(GetDocumentationSampleResource(t) + "/labels", true);
+      return;
+    }
+
+    assert(!call.GetFullUri().empty());
+    const std::string publicId = call.GetUriComponent("id", "");
+    ResourceType level = StringToResourceType(call.GetFullUri() [0].c_str());
+
+    std::set<std::string> labels;
+    OrthancRestApi::GetIndex(call).ListLabels(labels, publicId, level);
+
+    Json::Value result = Json::arrayValue;
+
+    for (std::set<std::string>::const_iterator it = labels.begin(); it != labels.end(); ++it)
+    {
+      result.append(*it);
+    }
+
+    call.GetOutput().AnswerJson(result);
+  }
+  
+
+  static void GetLabel(RestApiGetCall& call)
+  {
+    if (call.IsDocumentation())
+    {
+      ResourceType t = StringToResourceType(call.GetFullUri()[0].c_str());
+      std::string r = GetResourceTypeText(t, false /* plural */, false /* upper case */);
+      call.GetDocumentation()
+        .SetTag(GetResourceTypeText(t, true /* plural */, true /* upper case */))
+        .SetSummary("Test label")
+        .SetDescription("Test whether the " + r + " is associated with the given label")
+        .SetUriArgument("id", "Orthanc identifier of the " + r + " of interest")
+        .SetUriArgument("label", "The label of interest")
+        .AddAnswerType(MimeType_PlainText, "Empty string is returned in the case of presence, error 404 in the case of absence");
+      return;
+    }
+
+    CheckValidResourceType(call);
+
+    assert(!call.GetFullUri().empty());
+    const std::string publicId = call.GetUriComponent("id", "");
+    const ResourceType level = StringToResourceType(call.GetFullUri() [0].c_str());
+
+    std::string label = call.GetUriComponent("label", "");
+
+    std::set<std::string> labels;
+    OrthancRestApi::GetIndex(call).ListLabels(labels, publicId, level);
+    
+    if (labels.find(label) != labels.end())
+    {
+      call.GetOutput().AnswerBuffer("", MimeType_PlainText);
+    }
+  }
+
+
+  static void AddLabel(RestApiPutCall& call)
+  {
+    if (call.IsDocumentation())
+    {
+      ResourceType t = StringToResourceType(call.GetFullUri()[0].c_str());
+      std::string r = GetResourceTypeText(t, false /* plural */, false /* upper case */);
+      call.GetDocumentation()
+        .SetTag(GetResourceTypeText(t, true /* plural */, true /* upper case */))
+        .SetSummary("Add label")
+        .SetDescription("Associate a label with a " + r)
+        .SetUriArgument("id", "Orthanc identifier of the " + r + " of interest")
+        .SetUriArgument("label", "The label to be added");
+      return;
+    }
+
+    CheckValidResourceType(call);
+
+    std::string publicId = call.GetUriComponent("id", "");
+    const ResourceType level = StringToResourceType(call.GetFullUri() [0].c_str());
+
+    std::string label = call.GetUriComponent("label", "");
+    OrthancRestApi::GetIndex(call).ModifyLabel(publicId, level, label, StatelessDatabaseOperations::LabelOperation_Add);
+
+    call.GetOutput().AnswerBuffer("", MimeType_PlainText);
+  }
+
+
+  static void RemoveLabel(RestApiDeleteCall& call)
+  {
+    if (call.IsDocumentation())
+    {
+      ResourceType t = StringToResourceType(call.GetFullUri()[0].c_str());
+      std::string r = GetResourceTypeText(t, false /* plural */, false /* upper case */);
+      call.GetDocumentation()
+        .SetTag(GetResourceTypeText(t, true /* plural */, true /* upper case */))
+        .SetSummary("Remove label")
+        .SetDescription("Remove a label associated with a " + r)
+        .SetUriArgument("id", "Orthanc identifier of the " + r + " of interest")
+        .SetUriArgument("label", "The label to be removed");
+      return;
+    }
+
+    CheckValidResourceType(call);
+
+    std::string publicId = call.GetUriComponent("id", "");
+    const ResourceType level = StringToResourceType(call.GetFullUri() [0].c_str());
+
+    std::string label = call.GetUriComponent("label", "");
+    OrthancRestApi::GetIndex(call).ModifyLabel(publicId, level, label, StatelessDatabaseOperations::LabelOperation_Remove);
+
+    call.GetOutput().AnswerBuffer("", MimeType_PlainText);
+  }
+  
 
   // Handling of attached files -----------------------------------------------
 
@@ -3854,6 +3977,12 @@
       Register("/" + resourceTypes[i] + "/{id}/metadata/{name}", GetMetadata);
       Register("/" + resourceTypes[i] + "/{id}/metadata/{name}", SetMetadata);
 
+      // New in Orthanc 1.12.0
+      Register("/" + resourceTypes[i] + "/{id}/labels", ListLabels);
+      Register("/" + resourceTypes[i] + "/{id}/labels/{label}", GetLabel);
+      Register("/" + resourceTypes[i] + "/{id}/labels/{label}", RemoveLabel);
+      Register("/" + resourceTypes[i] + "/{id}/labels/{label}", AddLabel);
+
       Register("/" + resourceTypes[i] + "/{id}/attachments", ListAttachments);
       Register("/" + resourceTypes[i] + "/{id}/attachments/{name}", DeleteAttachment);
       Register("/" + resourceTypes[i] + "/{id}/attachments/{name}", GetAttachmentOperations);

--- a/OrthancServer/Sources/ServerContext.cpp	Mon Apr 03 18:09:04 2023 +0200
+++ b/OrthancServer/Sources/ServerContext.cpp	Mon Apr 03 20:53:14 2023 +0200
@@ -2144,6 +2144,16 @@
 
     }
 
+    {
+      Json::Value labels = Json::arrayValue;
+
+      for (std::set<std::string>::const_iterator it = resource.labels_.begin(); it != resource.labels_.end(); ++it)
+      {
+        labels.append(*it);
+      }
+
+      target["Labels"] = labels;
+    }
   }