API group labels
What does this MR do?
Implements the groups labels API.
What are the relevant issue numbers?
Closes #44901 (closed)
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Documentation created/updated
- Tests added for this feature/bug
- Conforms to the code review guidelines
- Conforms to the merge request performance guidelines
- Conforms to the style guides
- Conforms to the database guides