The key that identifies the localized string to use for the alert message.
- iOS 8.0+
- macOS 10.10+
- Mac Catalyst 13.0+
- watchOS 3.0+
When delivered to your app, the push notification gets the text for the alert by looking up the specified key in your app’s
Localizable file. When this property is set, the value in the
init(from property is ignored.