Background Push Demo

1. In app.json and Info.plist, replace the bundle identifier (com.merkle-manufactory.background-push-demo) with a unique value.
2. Run yarn install to install dependencies.
3. Plug in a physical iPhone via USB.
4. Run yarn ios, and choose the physical device to build the app.
5. Visit App Store Connect and create a new iOS app with the new bundle ID. Be sure to enable the Push Notification capability.
6. Run yarn ios to rebuild the app.
7. Enable push notifications via the app's UI.
8. Long-press the device token and copy to clipboard.
9. Visit the Apple Push Notification Console, and navigate to the new push notification form.
10. Paste the copied device token, and with the app foregrounded, send a normal alert notification.
11. Observe setNotificationHandler#handleNotification, addNotificationReceivedListener, and setNotificationHandler#handleSuccess in the console logs, indicating that the app is receiving the notification.
12. Start a new test push form in the Apple Push Notification Console. Paste the device token, and with the app backgrounded, send a background notification (i.e. change the apns-push-type to background, which will add content-available: 1 to the payload).
13. Observe backgroundNotificationTask in the console logs, indicating that the app is receiving the notification.
14. Return once more to the Apple Push Notification Console to create a new push notification. Send a background notification to the device, but this time with the app in the foreground.
15. Observe that there are no logs from setNotificationHandler#handleNotification, addNotificationReceivedListener, addNotificationResponseReceivedListener, or backgroundNotificationTask.