Describe the bug
If I assign some user to a group (a user without policies attached), and this group has some policy attached, the policies don't affect the user.

This behavior doesn't happen if the user has at least 1 policy attached (even if the user-policy is not related to the group-policy)

To Reproduce
Steps to reproduce the behavior:

1. Start an empty RustFS instance.
2. Login as admin and create a user.
3. Attach the user to a group.
4. Attach some policy to the group (e.g. consoleAdmin).
5. Try to perform any action with the user account (e.g. list buckets).

Expected behavior
The user attached to a group should follow the group policies, even if the user has no policy attached individually.

Desktop:

• OS: Ubuntu 24.04
• Browser Brave 1.82.172
• Version RustFS 1.0.0-alpha.65