Add group_level? and instance_level? helpers to service.rb model
The following discussion from !57381 should be addressed:
- [ ] @arturoherrero started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/57381#note_537307639): (+2 comments)
> This is really nice! Finally, our vocabulary matches the code.
> I guess we should also add `instance_level?` and `group_level?` at some point. I was using: `service.instance?`, `service.group_id` or `service.project?` but this looks better.
issue