Merge branch 'troubleshoot-user-access' into 'master'

Add KAS troubleshooting section for unauthorized user

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127106



Merged-by: Phillip Wells <pwells@gitlab.com>
Reviewed-by: Viktor Nagy (GitLab) <vnagy@gitlab.com>
Co-authored-by: Timo Furrer <tfurrer@gitlab.com>