ISTWCMS-5254: Use mb_strtolower() in AD group name comparison

uw_cfg_common.module

@@ -982,16 +982,16 @@ function uw_cfg_common_webform_access(WebformInterface $webform, string $operati
       // Access control by Active Directory group.
       // Convert all groups to lowercase for case-insensitive matching.
       $user_ad_groups = uw_cfg_common_get_user_ad_groups() ?: [];
-      $user_ad_groups = array_map('strtolower', $user_ad_groups);
+      $user_ad_groups = array_map('mb_strtolower', $user_ad_groups);
       // Required group. If at least one is provided, the user must be in it.
       $ad_require_groups = $webform->getThirdPartySetting('uw_cfg_common', 'ad_require_groups');
-      $ad_require_groups = array_map('strtolower', $ad_require_groups);
+      $ad_require_groups = array_map('mb_strtolower', $ad_require_groups);
       if ($ad_require_groups && !array_intersect($ad_require_groups, $user_ad_groups)) {
         return AccessResult::forbidden();
       }
       // Deny group. If at least one is provided, the user must not be in it.
       $ad_deny_groups = $webform->getThirdPartySetting('uw_cfg_common', 'ad_deny_groups');
-      $ad_deny_groups = array_map('strtolower', $ad_deny_groups);
+      $ad_deny_groups = array_map('mb_strtolower', $ad_deny_groups);
       if ($ad_deny_groups && array_intersect($ad_deny_groups, $user_ad_groups)) {
         return AccessResult::forbidden();
       }