website/integrations: Add instructions for Mattermost Team Edition

[pacohope]

Details

These instructions explain how to use authentik with Mattermost Team Edition. It's a bit of a hack, since it leverages the GitLab integration. But it works. I have this running on 2 different authentik/mattermost pairs. One is Mattermost 10.5.1 with authentik 2024.12.3, and the other is Mattermost 10.8.1 with authentik 2025.4.1 (latest versions of each).

I know authentik documentation tends to be pretty minimal: only the absolutely required details. But with a chat system like Mattermost, I thought it important to show how to customize the userid. I have marked it optional.

---

If applicable

• [x] The documentation has been updated
• [x] The documentation has been formatted (make website)

[netlify[bot]]

❌ Deploy Preview for authentik-docs failed. Why did it fail? →

Name	Link
🔨 Latest commit	f8092792cc5e6f72104c70bb29fab70bf07545d7
🔍 Latest deploy log	https://app.netlify.com/projects/authentik-docs/deploys/683c5ee51924f400081bdb57

[netlify[bot]]

✅ Deploy Preview for authentik-storybook canceled.

Name	Link
🔨 Latest commit	f8092792cc5e6f72104c70bb29fab70bf07545d7
🔍 Latest deploy log	https://app.netlify.com/projects/authentik-storybook/deploys/683c5ee57759b80008fbe697

[pacohope]

Thanks for the help. I will definitely get back to this, so please don't close it for being idle. I tend to do this sort of thing on the weekends, so I may be a little slow to integrate the feedback. As soon as I saw build errors I realized (a) I should tool up and get the web site building working, and (b) I hadn't linked it in anywhere like the integration sidebar that you mentioned. So I'll get back to that this weekend.

[dominic-r]

Sure, take all the time you need! No worries.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 92.77%. Comparing base (8750551) to head (f809279). :warning: Report is 790 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14802      +/-   ##
==========================================
+ Coverage   92.76%   92.77%   +0.01%     
==========================================
  Files         817      817              
  Lines       42197    42197              
==========================================
+ Hits        39142    39148       +6     
+ Misses       3055     3049       -6     

Flag	Coverage Δ
e2e	47.56% <ø> (+<0.01%)	:arrow_up:
integration	24.38% <ø> (ø)
unit	90.66% <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.

:rocket: New features to boost your workflow:

• :package: JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.