Issue #2827084 by damiankloip, Wim Leers, dawehner, prics, larowlan, catch,...

Issue #2827084 by damiankloip, Wim Leers, dawehner, prics, larowlan, catch, darrenwh: EntityNormalizer::denormalize should not throw UnexpectedValueException, but \Symfony\Component\HttpKernel\Exception\UnprocessableEntityHttpException, so we get a 422 response instead of 400