website/integrations: gitlab: add oidc guide

[motey]

Details

Adding a guide to connect GitLab via OIDC (alternative to SAML which is the only guide at the moment)

Discussed in:

Closes #8175

---

Checklist

• [ ] Local tests pass (ak test authentik/) <- not applicable; only doc changes
• [ ] The code has been formatted (make lint-fix) <- not applicable; only doc changes

If an API change has been made

• [ ] The API schema has been updated (make gen-build) <- not applicable; only doc changes

If changes to the frontend have been made

• [ ] The code has been formatted (make web) <- not applicable; only doc changes

If applicable

• [x] The documentation has been updated
• [x] The documentation has been formatted (make website) <- Yes, but very unsure about this. should that not happen on "server"-side (github actions) in a controlled environment. Needed to install a lot of stuff on my machine for that :D not very contributor friendly

[netlify[bot]]

✅ Deploy Preview for authentik-storybook ready!

Name	Link
🔨 Latest commit	82dfd92d70478294a6d76e5d1e75ddbb51739f09
🔍 Latest deploy log	https://app.netlify.com/sites/authentik-storybook/deploys/667291cebc972b00082f5285
😎 Deploy Preview	https://deploy-preview-9740--authentik-storybook.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[netlify[bot]]

✅ Deploy Preview for authentik-docs ready!

Name	Link
🔨 Latest commit	82dfd92d70478294a6d76e5d1e75ddbb51739f09
🔍 Latest deploy log	https://app.netlify.com/sites/authentik-docs/deploys/667291cf22ff6e0008ea86ef
😎 Deploy Preview	https://deploy-preview-9740--authentik-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.28%. Comparing base (ae97eac) to head (82dfd92). Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9740      +/-   ##
==========================================
- Coverage   92.62%   92.28%   -0.35%     
==========================================
  Files         712      712              
  Lines       34924    34924              
==========================================
- Hits        32350    32229     -121     
- Misses       2574     2695     +121     

Flag	Coverage Δ
e2e	48.21% <ø> (-1.38%)	:arrow_down:
integration	25.41% <ø> (ø)
unit	90.10% <ø> (+<0.01%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[motey]

@tanberry sorry, i am a little bit confused what the state of this PR is now and whose turn it is to act now :) maybe you can help out. thanks.