Fixed sorting on talk chats

lib/api/marianumcloud/talk/room/getRoomResponse.dart

@@ -15,20 +15,22 @@ class GetRoomResponse extends ApiResponse {
   Map<String, dynamic> toJson() => _$GetRoomResponseToJson(this);
 
   List<GetRoomResponseObject> sortBy({bool lastActivity = true, required bool favoritesToTop, required bool unreadToTop}) {
-    return data.toList()..sort((a, b) {
+    for (var chat in data) {
+      final buffer = StringBuffer();
 
-      // Unread messages
+      if(favoritesToTop) {
+        buffer.write(chat.isFavorite ? "b" : "a");
+      }
       if(unreadToTop) {
-        int unreadStatus = b.unreadMessages.compareTo(a.unreadMessages);
-        if(unreadStatus != 0) return unreadStatus;
+        buffer.write(chat.unreadMessages > 0 ? "b" : "a");
       }
 
-      // Favorites
-      if(favoritesToTop) if(a.isFavorite) return -1;
+      buffer.write(chat.lastActivity);
 
-      // Activity
-      return b.lastActivity.compareTo(a.lastActivity);
-    });
+      chat.sort = buffer.toString();
+    }
+
+    return data.toList()..sort((a, b) => b.sort!.compareTo(a.sort!));
   }
 }
 
@@ -64,6 +66,7 @@ class GetRoomResponseObject {
   String? status;
   String? statusIcon;
   String? statusMessage;
+  String? sort;
 
   GetRoomResponseObject(
       this.id,