* Add consumable invites
* Add UI for generating invite codes
* Add tests
* Display max uses and expiration in invites table, delete invite
* Remove unused column and redundant validator
- Default follows not used, probably bad idea
- InviteCodeValidator is redundant because RegistrationsController
checks invite code validity
* Add admin setting to disable invites
* Add admin UI for invites, configurable role for invite creation
- Admin UI that lists everyone's invites, always available
- Admin setting min_invite_role to control who can invite people
- Non-admin invite UI only visible if users are allowed to
* Do not remove invites from database, expire them instantly
* Add overview of active sessions
* Better display of browser/platform name
* Improve how browser information is stored and displayed for sessions overview
* Fix test
An attempt to open a brand new Mastodon instance configured
as SINGLE_USER_MODE=true will cause an exception.
Enable temporary registration if we have no users in the database
Fixes#1817
Eugen Rochko