Currently WebSocket in WebFlux with Netty only allows frames that are not over 65536 bytes (in NettyWebSocketSessionSupport#DEFAULT_FRAME_MAX_SIZE)
It would be nice if we can override the default value.
Affects: 5.0.1, 5.0.8
#20933 Upgrade to Reactor Netty 0.8 ("depends on")
spring-projects#20776 added the ability to set max frame size for netty websocket support.
This PR adds the ability to override `createWebSocketSession()` to the new constructor may be called. Users want to be able to do this in Spring Cloud Gateway. Rather than overriding all of execute, we only have to override creation of the class.