code: public static synchronized void sse(String url) {
          checkStarted();
          instance().endpoints.add(HandlerUtil.sse(url, null));
      }
docs: Define a Server sent events endpoint without a handler. Supports path variables
  Data can be broadcast to this endpoint by using {@link io.joshworks.snappy.sse.SseBroadcaster}
  
  @param url The relative URL to be map this endpoint.