Support handling javax.validation.ConstraintViolationException

[nicmunroe]

If a spring controller is annotated with @org.springframework.validation.annotation.Validated, an endpoint argument is annotated with JSR 303 validation annotations (e.g. @Valid @NotBlank(message = "SOME_API_ERROR") @RequestParam(name = "fooParam") String fooParam), and a request comes in that violates those JSR 303 annotations, then yet another codepath is executed that ends up causing a javax.validation.ConstraintViolationException to be thrown.

We could handle this in backstopper with ClientDataValidationErrorHandlerListener, as the intention is the same and ClientDataValidationErrorHandlerListener is already setup to deal with the same ConstraintViolations that ConstraintViolationException contains. The result would have less info in the backstopper log message, but it would at least be handled properly instead of falling through to the generic 500 fallback handler.

NOTE: We'd need to make sure that the reusable JSR 303 convention tests cover this case (JSR 303 annotations on arbitrary method arguments) as well as the normal model object case.