Add visibility changes of project to the audit logs

• Zendesk ticket: https://gitlab.zendesk.com/agent/tickets/14657

Requested feature

Sometimes, for auditing reasons, it might be good to find out when the visibility of a project has been changes and by whom. This could be added to the audit log that we already have for important action that happen on a project.

Concrete questions / Next steps

@JobV what do you think?

/cc @dblessing

Good idea.

Milestone changed to 8.7

Milestone changed to 8.8

Added audit events label

mentioned in issue #579

Milestone changed to Backlog

mentioned in issue #251

Any idea of ETA on this? Also, note the requirement applies for group visibility changes, not just project changes.