Most of this documentation is great and should definitely be included. Many items are “self explanatory” but when something doesn’t work even experienced admins will find themselves reading values more than once wondering if they might affect their problem.
The Gitlab SSO area could use some improvement however. As I noted on the repo commit there is some ambiguity about what URL is desired there, especially when there is more than one possibility as in when SSL and/or a public facing proxy is involved.