def create_legacy_url
      if active_record_5_1?
        former_urlname = urlname_before_last_save
      else
        former_urlname = urlname_was
      end
      legacy_urls.find_or_create_by(urlname: former_urlname)
    end
def create_legacy_url
      if active_record_5_1?
        former_urlname = urlname_before_last_save
      else
        former_urlname = urlname_was
      end
      legacy_urls.find_or_create_by(urlname: former_urlname)
    end
Stores the old urlname in a LegacyPageUrl