[#2323] Fixed a typo causing /accounts/relationships to render default relationships. Improved the tests.

Ensured no auxiliary computations (actors list preparation etc.) related to relationships preloading if no user is present (for statuses / accounts / relationships rendering).

Applied relationships preloading to GET /api/v1/accounts/relationships. Refactoring (User.binary_id/1).

Implemented preloading of relationships with parent activities' actors for statuses/timeline rendering. Applied preloading for notifications rendering. Fixed announces rendering issue (preloading-related).

Preloading of follow relations for timeline/statuses rendering (performance improvement). Refactoring.

Closes: pleroma/pleroma#1643

The hack with caching the follow relationship was introduced
when we still were storing it inside the follow activity, resulting in
slow queries. Now we store follow state in `FollowRelationship` table,
so this is no longer necessary.

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\/>'

This reverts merge request !1737

Hakaba Hitoyo authored Sep 26, 2019 and kaniini committed Sep 26, 2019

This reverts commit 3aef4bdf.

Mastodon API: Add a setting to hide follow/follower count from the user view (`hide_follows_count` and `hide_followers_count`)

followers/following is enabled

We are already doing that in AP representation, so I think we should do
it here as well for consistency.

`User.profile_url` already fallbacks to ap_id

Fixes #1165

Closes #1000