[enhancement]: Implement Phase 8 of the multiuser implementatoin plan

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Contact Details

_No response_

### What should this feature add?

Begin the process of writing the user, API and administrator's guides to the new multiuser feature, as documented in `docs/multiuser/`.

### Alternatives

_No response_

### Additional Content

_No response_