When getting the groups list via the API, only super users can get the group list including invite-only groups.
This change adds a new permission under groups that can be granted to any user that includes all invite-only groups (except hidden groups) into the groups list requested by the user. This, however, does not allow the user to access all invite-only groups; only that they show up on the groups list page and related API requests.

Added a unit test, which passes (along with all other tests). The test checks that an invite-only group that a user is not a part of becomes viewable to the user once they are given the new permission. The test also checks that the permission does not give the user default access to invite-only hidden groups.