Mastodon API: do not create a following relationship if the corresponding follow request doesn't exist when calling `POST /api/v1/follow_requests/:id/authorize`

Closes #1497

This fixes race conditions.

FollowingRelationship storage & performance optimizations (state turned `ecto_enum`-driven integer, reorganized indices etc.).

Done via the following command:
git diff fcd5dd25 --stat --name-only | xargs sed -i '/Pleroma Authors/c# Copyright © 2017-2020 Pleroma Authors <https:\/\/pleroma.social\/>'

Tweaks to `clear_config` calls in tests in order to prevent side effects on config during test suite execution.

[#1335] Reorganized users.subscribers as UserRelationship. Added tests for UserRelationship-related functionality.

[#1335] Implemented notification mutes and reblog mutes as UserRelationships. User to UserRelationship relations and functions refactoring.

lain authored Oct 05, 2019 and kaniini committed Oct 05, 2019

This saves us lots of sending out because we can use sharedInbox.

This saves us lots of sending out because we can use sharedInbox.