Use serialization groups for triggering purge

[shule727]

It would be useful if serialization groups could be used to purge routes when theirs properties change.

E.g.

@PurgeOn(Post::class, groups={"common"})

Also, it would be useful for Purgatory to be able to automatically use FOSRest and API Platform groups defined in the PHPDoc if not explicitly given as parameter to PurgeOn.