[Webhook] decouple the Webhook component from the Serializer component

[fabpot]

Q	A
Feature PR	symfony/symfony#57881
PR author(s)	@xabbuh
Merged in	7.2

We created this issue to not forget to document this new feature. We would really appreciate if you can help us with this task. If you are not sure how to do it, please ask us and we will help you.

To fix this issue, please create a PR against the 7.2 branch in the symfony-docs repository.

Thank you! 😃

[MrYamous]

Webhook documentation doesn't mention Serializer as a requirement, I think there is no change to do for 7.2
But event if it is an undesirable behaviour what about adding a note for previous versions ?