code: public ServerListenerBuilder addStartedCallbacks(Iterable<Consumer<? super Server>> consumers) {
          requireNonNull(consumers, "consumers");
          for (Consumer<? super Server> consumer : consumers) {
              serverStartedCallbacks.add(requireNonNull(consumer, "consumer"));
          }
          return this;
      }
docs: Add {@link Consumer}s invoked when the {@link Server} is started.
  (see: {@link ServerListener#serverStarted(Server)})