Support global @MessageExceptionHandler via @ControllerAdvice in RSocket

[kitkars]

This is specific to rSocket.

Add support for global @MessageExceptionHandler using @ControllerAdvice.
Currently @MessageExceptionHandler needs to be part of same controller to handle issues.

[rstoyanchev]

@ControllerAdvice and ControllerAdviceBean are in spring-web unfortunately and spring-messaging cannot depend on that.

What we could do however is expose a method in RSocketMessageHandler to accept MessagingAdviceBean registrations, which is an interface that can be implemented as a simple wrapper/delegate around a ControllerAdviceBean. That leaves only a small amount of glue code to be done by the application:

ControllerAdviceBean.findAnnotatedBeans(context).forEach(controllerAdviceBean ->
        rsocketMessageHandler.registerAdviceBean(new MessagingAdviceBeanWrapper(controllerAdviceBean));

Spring Boot can probably do that automatically in its RSocketMessagingAutoConfiguration.