CLI tools for group management
TODO:
[x] Model Tests,
[ ] Jobs tests,
[ ] LDAP backend and tests,
[x] Checking Group::emailExists() when creating a user/alias
[x] Suspending a group when suspending a user (idea abandoned for now)
[ ] Removing a group member when removing a user?
[x] Deleting a user should delete groups
[x] force-deleting a group should remove entitlement records
[x] Limit "owner" of a "group" to be the same owner as the domain in which the group is to exist (could be automatic).
[x] Limits groups to custom (non-public) domains.