code refactoring

--- ./lib/private/User/Manager.php	2023-02-03 17:18:44.729561986 +0530

+++ ./lib/private/User/Manager-new.php	2023-02-09 19:35:34.309722378 +0530

@@ -705,6 +705,19 @@

+++ ./lib/private/User/Manager-new.php	2023-02-09 19:53:49.539733394 +0530

@@ -705,6 +705,20 @@

 	 * @since 9.1.0

 	 */

 	public function getByEmail($email) {

+		$uid=$email; // get first part of email if it contains alt domain, otherwise it is just $email

+		$alt_domain = $this->config->getSystemValue('alt_mail_domain', '');

+		if (isset($alt_domain)) {

+			$alt_domain_suffix = !empty($alt_domain) ? '@'  . $alt_domain : '';

+		$alt_domain_suffix ='';

+		if (isset($alt_domain) && !empty($alt_domain)) {

+			$alt_domain_suffix ='@'  . $alt_domain;

+		}

+

+		if (stristr($email, $alt_domain_suffix) !== FALSE) {

+			$uid = str_replace($alt_domain_suffix, '', $email);

+		}

+

+		}

+		if ($this->get($uid)) {

+			return([$this->get($uid)]);

+		}