Extend audit events API for groups
We added the first iteration of the Audit Events API in #121 (closed). However, this endpoint is only usable by a self-managed administrator - limiting its utility for GitLab.com, where most users are Owners without admin rights.
We should iterate on our Audit Event API and extend our API to the group level:
- Introduce endpoints that allow a group Owner to retrieve relevant audit events for groups and projects in the group.