feat: Added new API endpoint

packages/stream_chat/lib/src/client.dart

@@ -1347,6 +1347,18 @@ class StreamChatClient {
     return decode(response.data, UpdateMessageResponse.fromJson);
   }
 
+  /// Partially update the given message
+  /// Use 'set' in map to set values
+  /// User 'unset' in map to unset values
+  Future<UpdateMessageResponse> partiallyUpdateMessage(
+      String id, Map data) async {
+    final response = await put(
+      '/messages/${id}',
+      data: data,
+    );
+    return decode(response.data, UpdateMessageResponse.fromJson);
+  }
+
   /// Deletes the given message
   Future<EmptyResponse> deleteMessage(Message message) async {
     final response = await delete('/messages/${message.id}');
@@ -1385,20 +1397,21 @@ class StreamChatClient {
           )
           .toUtc();
     }
-    return updateMessage(
-      message.copyWith(
-        pinned: true,
-        pinExpires: pinExpires,
-      ),
-    );
+    return partiallyUpdateMessage(message.id, {
+      'set': {
+        'pinned': true,
+        if (pinExpires != null) 'pin_expires': pinExpires.toIso8601String(),
+      }
+    });
   }
 
   /// Unpins provided message
-  Future<UpdateMessageResponse> unpinMessage(Message message) => updateMessage(
-        message.copyWith(
-          pinned: false,
-        ),
-      );
+  Future<UpdateMessageResponse> unpinMessage(Message message) =>
+      partiallyUpdateMessage(message.id, {
+        'set': {
+          'pinned': false,
+        }
+      });
 }
 
 /// The class that handles the state of the channel listening to the events