message: Gitlab Enterprise documentation
  Most importantly documents the Gitlab callback URL but also the various scopes that seem appropriate.
diff: @@ -52,9 +52,27 @@ export AUTH_GITHUB_ENTERPRISE_INSTANCE_URL=https://x
  ### Gitlab
  +#### Creating a Gitlab Enterprise OAuth application
  +
  +Follow this link, substituting `gitlab.example.com` for your Gitlab enterprise domain, https://gitlab.example.com/profile/applications
  +
  +1. Set Application Name to `backstage-dev` or something along those lines.
  +1. The Authorization Callback URL should match the redirect URI set in Backstage.
  + 1. Set this to `http://localhost:7000/api/auth/gitlab/handler/frame` for local development.
  + 1. Set this to `http://{APP_FQDN}:{APP_BACKEND_PORT}/api/auth/gitlab/handler/frame` for non-local deployments.
  + 1. Select the checked scopes from this list:
  + - [ ] `api` Grants complete read/write access to the API, including all groups and projects.
  + - [x] `read_user` Grants read-only access to the authenticated user's profile through the /user API endpoint, which includes username, public email, and full name. Also grants access to read-only API endpoints under /users.
  + - [x] `read_repository` Grants read-only access to repositories on private projects using Git-over-HTTP (not using the API).
  + - [x] `write_repository` Grants read-write access to repositories on private projects using Git-over-HTTP (not using the API).
  + - [ ] `sudo` Grants permission to perform API actions as any user in the system, when authenticated as an admin user.
  + - [x] `openid` Grants permission to authenticate with GitLab using OpenID Connect. Also gives read-only access to the user's profile and group memberships.
  + - [x] `profile` Grants read-only access to the user's profile data using OpenID Connect.
  + - [x] `email` Grants read-only access to the user's primary email address using OpenID Connect.
  +
  ```bash
  -export GITLAB_BASE_URL=x # default is https://gitlab.com
  -export AUTH_GITLAB_CLIENT_ID=x
  +export GITLAB_BASE_URL=https://gitlab.example.com # for GitLab Enterprise. default is https://gitlab.com
  +export AUTH_GITLAB_CLIENT_ID=x # Gitlab calls this the Application ID
  export AUTH_GITLAB_CLIENT_SECRET=x
  ```
  