fix: Do not set old events as state events

Previously we had a check which uses the old
sortOrder value.
This check has been removed with the refactoring which leads to
bug #209. This fixes it by checking if the
event is already known in the database.
I am not 100% happy with this solution as this database api is impossible
to be implemented with a sqlite db. Once we start to refactor the whole sync update logic
we maybe could find a better way, but only the fox god knows.

lib/src/database/database_api.dart

@@ -69,6 +69,8 @@ abstract class DatabaseApi {
 
   Future<Event?> getEventById(int clientId, String eventId, Room room);
 
+  bool eventIsKnown(int clientId, String eventId, String roomId);
+
   Future<void> forgetRoom(int clientId, String roomId);
 
   Future<void> clearCache(int clientId);

lib/src/database/hive_database.dart

@@ -344,6 +344,10 @@ class FamedlySdkHiveDatabase extends DatabaseApi {
     return Event.fromJson(convertToJson(raw), room);
   }
 
+  @override
+  bool eventIsKnown(int clientId, String eventId, String roomId) =>
+      _eventsBox.keys.contains(MultiKey(roomId, eventId).toString());
+
   /// Loads a whole list of events at once from the store for a specific room
   Future<List<Event>> _getEventsByIds(List<String> eventIds, Room room) =>
       Future.wait(eventIds

lib/src/room.dart

@@ -336,6 +336,15 @@ class Room {
       return;
     }
 
+    // Do not set old events as state events
+    final prevEvent = getState(state.type, state.stateKey);
+    if (prevEvent != null &&
+        prevEvent.eventId != state.eventId &&
+        client.database != null &&
+        client.database.eventIsKnown(client.id, state.eventId, state.roomId)) {
+      return;
+    }
+
     states[state.type] ??= {};
     states[state.type][state.stateKey ?? ''] = state;
   }