I have a small problem with the notification message shown on the device when the pass is updated. I want the message to be what I set in the
%@ is present in the message, you will only ever see the generic message "Coupon Changed" that you have described.
If you do not want the field value to show then you can include the message you want then pad with spaces before ending in
%@. The spaces will ensure that the value is not shown on the lock screen and should help achieve your goal.