No way to receive close status with WebSocketInbound

[rstoyanchev]

WebsocketInbound provides Flux<WebSocketFrame> receiveFrames() which turns CloseWebSocketFrame into a completion signal, but a result there is no way to receive the close status and reason sent by the remote peer. This is asymmetric with WebSocketOutbound which does provide a way to send a close status and reason.

This same has been requested in SPR-17547 but in order to implement it there, we'd first need a way to get the close status through the Reactor Netty API.

[rstoyanchev]

One idea to consider, an extra method in WebSocketInbound:

/** 
  * Receive the close status code and reason if sent by the remote peer,
  * or empty if the connection completes otherwise.
  */
Mono<CloseStatus> receiveCloseStatus();