Issue #3046085 by kavbiswa, imalabya, joachim: Update deprecated Unicode::* to mb_*

 * Allows users to register with an email address as their username.

 */

use Drupal\Component\Utility\Unicode;

use Drupal\user\UserInterface;

use Drupal\Core\Render\Element\Email;

use Drupal\Core\Form\FormStateInterface;

  $name = ('' === $name) ? t('user') : $name;

  // Truncate to a reasonable size.

  $name = (Unicode::strlen($name) > (UserInterface::USERNAME_MAX_LENGTH - 10)) ? Unicode::substr($name, 0, UserInterface::USERNAME_MAX_LENGTH - 11) : $name;

  $name = (mb_strlen($name) > (UserInterface::USERNAME_MAX_LENGTH - 10)) ? mb_substr($name, 0, UserInterface::USERNAME_MAX_LENGTH - 11) : $name;

  return $name;

}