FEP-5219: Groups and permissions has been updated:

https://codeberg.org/fediverse/fep/pulls/895/files

- The items in the affiliations collection are now required to be full Relationship objects with id, attributedTo and object properties. I think these objects should be self-contained and exist independently of the collection.
- Access to the collection MAY be limited (for example, when the group is private).

#fep_5219