recordMessageEvent method
Implementation
@override
Future<void> recordMessageEvent(String topic, String message) async {
  final String hash = hashMessage(message);
  onCreate.broadcast(StoreCreateEvent(topic, {hash: message}));
  if (!data.containsKey(topic)) {
    data[topic] = {};
  }
  data[topic]![hash] = message;
  await persist();
}