public function getUpdatedValue()
{
$updated = \LockerRequest::header('Updated');
// Checks the updated parameter.
if (!empty($updated)) {
if (!$this->validateTimestamp($updated)) {
\App::abort(400, sprintf("`%s` is not an valid ISO 8601 formatted timestamp", $updated));
}
} else {
$updated = Carbon::now()->toISO8601String();
}
return $updated;
}