docs: add entra group name sync tutorial

[fstau]

Add tutorial: Microsoft Entra ID Group Name Sync

Summary

This PR adds a community tutorial explaining how to configure Microsoft Entra ID to return human-readable group names instead of GUIDs when using OAuth group synchronization with Open WebUI.

Background

I am working with a couple of organisations deploying Open WebUI internally that have run into issues with Microsoft Entra ID group synchronisation leading to GUIDs as Open WebUI group names when following default setup instructions. There are issues / discussions on the open-webui repository that describe troubleshooting steps and solutions. I have verified that those work to unblock my own deployments and created this writeup of the required steps to aid others trying to solve this issue via better discoverability in the docs.
This information was gathered from community discussion in open-webui/open-webui#13657.

Content

The tutorial covers:

• Step-by-step configuration of App Registration token claims
• Manifest modifications to enable cloud_displayname
• Enterprise Application group assignment requirements
• Required Open WebUI environment variables for OAuth group management
• Verification steps using jwt.ms
• Troubleshooting common issues (GUIDs still appearing, groups not syncing, JIT creation not working)
• Example Docker Compose configuration

Documentation Standards

• Includes community contribution warning
• Uses terminology consistent with official docs ("Microsoft Entra ID", "Just-in-Time (JIT) group creation")
• Cross-references relevant feature documentation (/features/auth/sso, /features/rbac/groups)

[pr-validator-bot]

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[Classic298]

LGTM thanks!