Merge branch 'julianthome-master-patch-34361' into 'master'

Add section about the user/group permissions to the handbook.

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/175852



Merged-by: Russell Dickenson <rdickenson@gitlab.com>
Approved-by: Thiago Figueiró <tfigueiro@gitlab.com>
Approved-by: Russell Dickenson <rdickenson@gitlab.com>
Co-authored-by: Julian Thome <jthome@gitlab.com>