[Web] Use INTL_IDNA_VARIANT_UTS46 in idn_to_ascii (thanks to @Knight1 !)

[Web] Some PHP fixes (warnings, notices)
[Web] Add quota notification tools

data/web/json_api.php

@@ -1161,6 +1161,9 @@ if (isset($_SESSION['mailcow_cc_role']) || isset($_SESSION['pending_mailcow_cc_u
           case "quarantine":
             process_edit_return(quarantine('edit', $attr));
           break;
+          case "quota_notification":
+            process_edit_return(quota_notification('edit', $attr));
+          break;
           case "mailq":
             process_edit_return(mailq('edit', array_merge(array('qid' => $items), $attr)));
           break;