Add bookmarks (#7107)

* Add backend support for bookmarks

Bookmarks behave like favourites, except they aren't shared with other
users and do not have an associated counter.

* Add spec for bookmark endpoints

* Add front-end support for bookmarks

* Introduce OAuth scopes for bookmarks

* Add bookmarks to archive takeout

* Fix migration

* Coding style fixes

* Fix rebase issue

* Update bookmarked_statuses to latest UI changes

* Update bookmark actions to properly reflect status changes in state

* Add bookmarks item to single-column layout

* Make active bookmarks red

config/initializers/doorkeeper.rb

@@ -58,6 +58,7 @@ Doorkeeper.configure do
   optional_scopes :write,
                   :'write:accounts',
                   :'write:blocks',
+                  :'write:bookmarks',
                   :'write:conversations',
                   :'write:favourites',
                   :'write:filters',
@@ -71,6 +72,7 @@ Doorkeeper.configure do
                   :read,
                   :'read:accounts',
                   :'read:blocks',
+                  :'read:bookmarks',
                   :'read:favourites',
                   :'read:filters',
                   :'read:follows',