docs: protected final Mono<Void> shutdownServer(DisposableServer disposableServer) {
      return Mono.defer(
          () ->
              Optional.ofNullable(disposableServer)
                  .map(
                      server -> {
                        server.dispose();
                        return server
                            .onDispose()
                            .doOnError(e -> LOGGER.warn("Failed to close server: " + e))
                            .onErrorResume(e -> Mono.empty());
                      })
                  .orElse(Mono.empty()));
    }