feat(entoas): Support RequestGroups to determine what fields to serialize for the requestBody

[omarhachach]

If a better way to do it is available, feel free to let me know 😄

[omarhachach]

Do note: using RequestGroups on edges breaks ogent: https://github.com/ariga/ogent/blob/main/template/update.tmpl#L17 This is due to ogent assuming that all edges are present always, which they wont be anymore.