code: public static ServerSentEvent withEventId(ByteBuf eventId, ByteBuf data) {
          return new ServerSentEvent(eventId, null, data);
      }
docs: Creates a {@link ServerSentEvent} instance with an event id.
  
  @param eventId Id for the event.
  @param data Data for the event.
  
  @return The {@link ServerSentEvent} instance.