feat(serializer): check in child classes attribute's groups for serialization

[antoine-nedelec]

Q	A
Branch?	3.3
Tickets	N/A
License	MIT
Doc PR	N/A

Original issue created:

• https://github.com/api-platform/api-platform/issues/2669

Self contained repository for reproduction:

• https://github.com/antoine-nedelec/api-platform-issue-test

Overall logic:

• When fetching the groups for a serialization, there might be a group filled only for one child class. and not available in any parent attributes. The entity is then serialized as an IRI, but there could have been specific attributes to be serialized.

Remarks:

• Not sure if this behavior should be limited with a configuration as I did ?
• Name of the attribute to be defined ?