Resolve "GroupsController#activity.json is REALLY slow due to SQL"
What does this MR do?
This solves a classic N + 1 queries problem.
Does this MR meet the acceptance criteria?
- Changelog entry added
- All builds are passing
- Conform by the merge request performance guides
- Conform by the style guides
Branch has no merge conflicts with
master(if it does - rebase it please)
- Squashed related commits together
Closes #27395 (closed)