Is there an existing issue for this?

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Current Behavior

Docs: https://coder.com/docs/admin/external-auth#gitlab-self-managed
The CODER_EXTERNAL_AUTH_0_ID environment variable is used for internal reference. Set it with a value that helps you identify it. For example, you can use CODER_EXTERNAL_AUTH_0_ID="primary-github" for your GitHub provider.

The docs say it's for internal use. If you confgure this as the doc states: CODER_EXTERNAL_AUTH_0_ID="primary-gitlab"
This variable is actually used in the callback url in authentication for git lab

the default callback url in gitlab listed in the doc is:
https://your-gitlab.example.com/users/auth/gitlab/callback

When a user tries to authenctiate with gitlab Coder will connect with
https://your-gitlab.example.com/users/auth/**gitlab-primary**/callback
This will cause a error "The redirect URI included is not valid"

Relevant Log Output

Expected Behavior

Docs: https://coder.com/docs/admin/external-auth#gitlab-self-managed
Clearer explanation of the function of AUTH_0_ID

Steps to Reproduce

1.https://coder.com/docs/admin/external-auth#gitlab-self-managed
2. https://docs.gitlab.com/integration/oauth_provider/
3. Attempt authentication with a SAML tracer app to see AUTH_0_ID is used as part of the callback url

Environment

• Host OS:
• Coder version:

Additional Context

No response