/**
 * Set the ETag header in the response
 *
 * @param   string  $etag  The entity tag (etag) to set
 *
 * @return  void
 *
 * @since   1.7.0
 */
protected function _setEtag($etag)
{
    Factory::getApplication()->setHeader('ETag', '"' . $etag . '"', true);
}