public static RoutedMessage createHello(
     long version, String roomId, MediatorNexus.UserView user) {
   return new RoutedMessage(
       FlowTarget.roomHello,
       roomId,
       String.format(MSG_HELLO_JOIN, version, user.getUserId(), user.getUserName()));
 }
 public static RoutedMessage createPart(String roomId, MediatorNexus.UserView user) {
   return new RoutedMessage(
       FlowTarget.roomPart,
       roomId,
       String.format(MSG_PROTOCOL, user.getUserId(), user.getUserName()));
 }