add subresource resourceClass changes

Author: esserj

CHANGELOG.md

@@ -11,6 +11,7 @@
 * GraphQL: Support for field name conversion (serialized name) (#3455, #3516)
 * OpenAPI: Add PHP default values to the documentation (#2386)
 * Deprecate using a validation groups generator service not implementing `ApiPlatform\Core\Bridge\Symfony\Validator\ValidationGroupsGeneratorInterface` (#3346)
+* Subresources: subresource resourceClass can now be defined as a container parameter in XML and Yaml definitions
 
 ## 2.5.5