Add backend support for bookmarks

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

app/controllers/api/v1/statuses/bookmarks_controller.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+class Api::V1::Statuses::BookmarksController < Api::BaseController
+  include Authorization
+
+  before_action -> { doorkeeper_authorize! :write }
+  before_action :require_user!
+
+  respond_to :json
+
+  def create
+    @status = bookmarked_status
+    render json: @status, serializer: REST::StatusSerializer
+  end
+
+  def destroy
+    @status = requested_status
+    @bookmarks_map = { @status.id => false }
+
+    bookmark = Bookmark.find_by!(account: current_user.account, status: @status)
+    bookmark.destroy!
+
+    render json: @status, serializer: REST::StatusSerializer, relationships: StatusRelationshipsPresenter.new([@status], current_user&.account_id, bookmarks_map: @bookmarks_map)
+  end
+
+  private
+
+  def bookmarked_status
+    authorize_with current_user.account, requested_status, :show?
+
+    bookmark = Bookmark.find_or_create_by!(account: current_user.account, status: requested_status)
+
+    bookmark.status.reload
+  end
+
+  def requested_status
+    Status.find(params[:status_id])
+  end
+end