update custom keys to not be included in alert property

src/notifications/senders/AppleNotificationSender.ts

@@ -107,15 +107,21 @@ export class AppleNotificationSender {
           resolve();
         });
 
+        const customKeys = {
+          ...notificationAlertArguments.customKeys,
+        }
+        delete notificationAlertArguments.customKeys;
+
         // See https://developer.apple.com/documentation/usernotifications/generating-a-remote-notification
         // for notification payload examples
-        req.write(JSON.stringify({
+        const payload = JSON.stringify({
           aps: {
             alert: notificationAlertArguments,
             sound: "default"
           },
-          ...notificationAlertArguments.customKeys,
-        }));
+          customKeys,
+        });
+        req.write(payload);
         req.end();
       });
       return true;