Namespace NB (object_server) should implement get/put_object_acl

[guymguym]

Is your feature request related to a problem? Please describe. No Object ACL support for object MDs.

Describe the solution you'd like Explore compatibility options of identities and ACLs.

Describe alternatives you've considered Current alternative is to ignore put, and return a constant default user.

Additional context Followup of PR #6152 and Issue #6156