* Re-add follow recommendations API

    GET /api/v1/suggestions

Removed in 8efa081f21 due to Neo4J
dependency. The algorithm uses triadic closures, takes into account
suspensions, blocks, mutes, domain blocks, excludes locked and moved
accounts, and prefers more recently updated accounts.

* Track interactions with people you don't follow

Replying to, favouriting and reblogging someone you're not following
will make them show up in follow recommendations. The interactions
have different weights:

- Replying is 1
- Favouriting is 10 (decidedly positive interaction, but private)
- Reblogging is 20

Following them, muting or blocking will remove them from the list,
obviously.

* Remove triadic closures, ensure potential friendships are trimmed

Do not touch statuses_count on accounts table when mass-destroying
statuses to reduce load when removing accounts, same for
reblogs_count and favourites_count

Do not count statuses with direct visibility in statuses_count

Fix #828

One RSA keypair for all fabricated test accounts is enough

The service used to be named ResolveRemoteAccountService resolves local
accounts as well.

There was a test when some of the properties are invalid, but none when all
of them are valid.

* Introduce domains method to Account relation

Account had followers_domains method, which was excessively specific.
Let relation of Account have domains method instead.

* Move follow_mapping in Account to AccountInteractions

* Introduce shared examples for AccountAvatar inclusion

* Cover Account more

* Fix db:seed - only run some validations when the field was changed

* Add tests

* Added support for configurable reserved usernames

* Added reserved usernames from mastodon issue 1355

* Fix reserved usernames

* Move specs for account finder methods to concern spec

* Move account finder methods to concern

* Improve spec wording

* Use more explicit comparison to ensure correct return value

* Add coverage for .find_local! and .find_remote!

* Add some methods to the finder

* Use arel on matching_username method

* Avoid ternary in matching domain method

* Simplify finder methods

* Use an AccountFinder class to simplify lookup

This reverts commit 5135d609b7.

* Add rough outline of coverage needed for public timeline

* Specs for visibility, replies, boosts

* Specs for silenced account

* Specs for local_only option

* Specs for blocks and mutes

* Add tentative spec around including other silenced account statuses

* Add with_public_visibility scope

* Add simple coverage for tag_timeline

* Tag timeline includes replies

* Replace tag.statuses with a tagged_with scope in tag timeline method

* Use with_public_visibility in tag timeline

* Extract common scope between public and tag timelines to method

* Extract local domain check to local_only scope

* Extract local_only check to starting scope method

* Move list of excluded from timeline account ids to account model

* Simplify excluded accounts list on account model

* Only join accounts when needed

* Rename method for account specific filtering

* Extract method for account exclusions

* Fix bug where silenced accounts were not including statuses from other silenced accounts

* DRY up filter application from account or no account

* timeline_scope can be private

* Add spec showing that account can find its excluded accounts ids

* Add spec which fails if local_only does not have a left outer join

* rubocop

* Add admin/instances index action

* Add link to instances admin page

* View lists instances

* Instances, grouped by domain, ordered by count

* Use Account.remote scope

* Extract method: Account.by_domain_accounts

* Remove unused method #set_counters_maps from api controller

* Remove unused method #set_account_counters_maps from api controller

* Remove unused method Account#followers_domains

* Remove unused User.prolific scope

* Add mastodon:users:admins task to list all admin emails

* Use interpolated query style in Account.triadic_closures

* Coverage for Account.triadic_closures

* Remote spec for non-existent entry_classes helper method

This method no longer exists, and is handled by a local variable in a partial
instead.

* Remove spec for non-existent Account#ping! method

* When avatar/header are GIF, generate static versions.
Account API returns "avatar"/"avatar_static", "header"/"header_static"
Static version is the same as original for other cases
Web UI de-animates avatars in toots, lists of users

Fix #441, fix #596, prerequisite for #1064

* Fix JS test

* Add rake task to generate static avatars/headers from GIF ones, add test

* Consolidate webfinger string creation under Account#to_webfinger_s

* Introduce Account#local_username_and_domain for consolidation

* Clean up SQL output in Tag and Account search methods

* Add basic coverage for Tag.search_for

* Add coverage for Account.search_for

* Add coverage for Account.advanced_search_for

Checking reblog vs original status was happening in multiple places
across the app. For views, this logic was encapsulated in a helper
method named `proper_status` but in the other layers of the app, the
logic was duplicated.

Because the logic is used at all layers of the app, we extracted it into
a `Status#proper` method on the model and changed all uses of the logic
to use this method. There is now a single source of truth for this
condition.

We added test coverage to untested methods that got refactored.

Fix anchor tags in some wikipedia URLs being matches as a hashtag

as well as formatting of content

and atom feed generation to some extent, as well as the way mentions are
stored