Use a Generator for users in searchInGroups, type it as iterable

[come-nc]

Summary

Since this is a new method in 27 it’s the occasion to make use of a generator instead of an array

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [ ] Tests (unit, integration, api and/or acceptance) are included
• [ ] Screenshots before/after for front-end changes
• [ ] Documentation (manuals or wiki) has been updated or is not required
• [ ] Backports requested where applicable (ex: critical bugfixes)