The app delegate works alongside the app object to ensure your app interacts properly with the system and with other apps. Specifically, the methods of the app delegate give you a chance to respond to important changes. For example, you use the methods of the app delegate to respond to state transitions, such as when your app moves from foreground to background execution, and to respond to incoming notifications. In many cases, the methods of the app delegate are the only way to receive these important notifications.
Important: In order to implement all feature and callbacks from App Delegate you see in this plugin. we had to override and extend from IOS UnityAppController. This means, that when IOS Native App delegate is enabled, you can't use another plugin that wants to override UnityAppController. The result will be a plugins conflict.
To enable App Delegate you need to do the same set of actions as for any other API of IOS Native. Just go to the IOS Native Setting Editor and enable the App Delegate feature.
Note: Disabling App Delegate, will also disable User Notifications.