Spring MVC and WebFlux method validation support that also adapts `ConstraintViolation`s

[rstoyanchev]

Introduce support for method validation in Spring MVC and Spring WebFlux. This requires changes first at a lower level to enhance MethodValidationInterceptor infrastructure to adapt ConstraintViolations to MessageSourceResolvable errors, further aggregated into a BindingResult for cascaded violations on Object method parameters.

For the full scope of changes on this theme, see #30645.

[neroncap]

Hi! I'm interesting in make some custom validations for the entire @RequestHeader, i was testing this issue and is not possible. It is planned to be included in further versions?

[rstoyanchev]

Yes it is possible as indicated in the summary above, but the goal is to make it better integrated with Spring MVC and WebFlux, and easier to handle validation exceptions.

If you need help to make it work as it is currently, this is not the right place.