* Add confirmation step for email changes
This adds a confirmation step for email changes of existing users.
Like the initial account confirmation, a confirmation link is sent
to the new address.
Additionally, a notification is sent to the existing address when
the change is initiated. This message includes instruction to reset
the password immediately or to contact the instance admin if the
change was not initiated by the account owner.
Fixes#3871
* Add review fixes
* 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
