Add support for group display names in form validation

[daniel-beck]

Recreation of #172 with autotest coverage.

Testing done

Autotest so far

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

[daniel-beck]

@timja Is this something you could give a quick spin? The original submitter explained it was for Entra ID.

[timja]

LGTM:

All working fine.