Fix deprecation message

Using a string "HTTP_BAD_REQUEST" as a constant of the "Symfony\Component\HttpFoundation\Response" class is deprecated since API Platform 2.1 and will not be possible anymore in API Platform 3. Use the Symfony's custom YAML extension for PHP constants instead (i.e. "!php/const Symfony\Component\HttpFoundation\Response::HTTP_BAD_REQUEST").

Author: darthf1

core/errors.md

@@ -75,7 +75,7 @@ api_platform:
     exception_to_status:
         # The 4 following handlers are registered by default, keep those lines to prevent unexpected side effects
         Symfony\Component\Serializer\Exception\ExceptionInterface: 400 # Use a raw status code (recommended)
-        ApiPlatform\Core\Exception\InvalidArgumentException: 'HTTP_BAD_REQUEST' # Or a `Symfony\Component\HttpFoundation\Response`'s constant
+        ApiPlatform\Core\Exception\InvalidArgumentException: !php/const Symfony\Component\HttpFoundation\Response::HTTP_BAD_REQUEST
         ApiPlatform\Core\Exception\FilterValidationException: 400
         Doctrine\ORM\OptimisticLockException: 409