Add scheduled statuses (#9706)

Fix #340

app/serializers/rest/scheduled_status_serializer.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class REST::ScheduledStatusSerializer < ActiveModel::Serializer
+  attributes :id, :scheduled_at
+
+  has_many :media_attachments, serializer: REST::MediaAttachmentSerializer
+
+  def id
+    object.id.to_s
+  end
+end