code: public List<WebSocketExtension> offerWebSocketExtensions(WsResourceAddress address,
                                                               ExtensionHelper extensionHelper) {
          List<WebSocketExtension> list = new ArrayList<>();
  
          for(WebSocketExtensionFactorySpi factory : factoriesRO.values()) {
              WebSocketExtension extension = factory.offer(extensionHelper, address);
              if (extension != null) {
                  list.add(extension);
              }
          }
          return list;
      }
docs: Returns a list of extensions that want to be part of websocket request
  
  @param address WsResourceAddress to which a websocket connection is being attempted
  @param extensionHelper extension helper
  @return list of extensions that want to be part of the request