Add status references support

app/models/status_reference.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: status_references
+#
+#  id               :bigint(8)        not null, primary key
+#  status_id        :bigint(8)        not null
+#  target_status_id :bigint(8)        not null
+#  created_at       :datetime         not null
+#  updated_at       :datetime         not null
+#
+
+class StatusReference < ApplicationRecord
+  belongs_to :status
+  belongs_to :target_status, class_name: 'Status'
+
+  has_one :notification, as: :activity, dependent: :destroy
+
+  validate :validate_status_visibilities
+
+  def validate_status_visibilities
+    raise Mastodon::ValidationError, I18n.t('status_references.errors.invalid_status_visibilities') if [:public, :public_unlisted, :unlisted, :login].exclude?(target_status.visibility.to_sym)
+  end
+end