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

app/controllers/api/v1/bookmarks_controller.rb

@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+class Api::V1::BookmarksController < Api::BaseController
+  before_action -> { doorkeeper_authorize! :read, :'read:bookmarks' }
+  before_action :require_user!
+  after_action :insert_pagination_headers
+
+  respond_to :json
+
+  def index
+    @statuses = load_statuses
+    render json: @statuses, each_serializer: REST::StatusSerializer, relationships: StatusRelationshipsPresenter.new(@statuses, current_user&.account_id)
+  end
+
+  private
+
+  def load_statuses
+    cached_bookmarks
+  end
+
+  def cached_bookmarks
+    cache_collection(
+      Status.reorder(nil).joins(:bookmarks).merge(results),
+      Status
+    )
+  end
+
+  def results
+    @_results ||= account_bookmarks.paginate_by_max_id(
+      limit_param(DEFAULT_STATUSES_LIMIT),
+      params[:max_id],
+      params[:since_id]
+    )
+  end
+
+  def account_bookmarks
+    current_account.bookmarks
+  end
+
+  def insert_pagination_headers
+    set_pagination_headers(next_path, prev_path)
+  end
+
+  def next_path
+    api_v1_bookmarks_url pagination_params(max_id: pagination_max_id) if records_continue?
+  end
+
+  def prev_path
+    api_v1_bookmarks_url pagination_params(since_id: pagination_since_id) unless results.empty?
+  end
+
+  def pagination_max_id
+    results.last.id
+  end
+
+  def pagination_since_id
+    results.first.id
+  end
+
+  def records_continue?
+    results.size == limit_param(DEFAULT_STATUSES_LIMIT)
+  end
+
+  def pagination_params(core_params)
+    params.slice(:limit).permit(:limit).merge(core_params)
+  end
+end