SEC-2914: Support @AuthenticationPrincipal on @SubscribeMapping endpoints

Igor Kolomiets (Migrated from SEC-2914) said:

I'm using latest websocket/messaging related features of Spring Security 4 to secure my application's websocket messaging endpoints. We have many @SubscribeMapping annotated methods to provide request-response style of communication that need access to current authenticated user. Currently we do this to get authenticated user:

@SubscribeMapping("/foo")
public MyResponse foo(MyAuthenticationToken authenticationToken) {
MyUser user = authenticationToken.getPrincipal();
}

Naturally I'd like to use @AuthenticationPrincipal so we can do this:

@SubscribeMapping("/foo")
public MyResponse foo(@AuthenticationPrincipal MyUser user) {

}

But it looks like @AuthenticationPrincipal is only supported by @MessageMapping annotated methods. Can we have it work for those annotated with @SubscribeMapping?

Start by comparing how @AuthenticationPrincipal is supported for @MessageMapping methods with the @SubscribeMapping endpoints described in the issue. Trace the existing Spring Security messaging argument-resolution path, then verify that a principal can be injected for @SubscribeMapping methods using the requested example shape.