ios: Remove didReceiveRemoteNotification method override in AppDelegate

Apple's documentation for this UIApplication method
  ( https://developer.apple.com/documentation/uikit/uiapplicationdelegate/1623013-application )
says at the top:

> Tells the app that a remote notification arrived that indicates
> there is data to be fetched.

From experimentation, it turns out that the qualifier "that
indicates…" is quite important! It seems to mean that the method
won't be called except for "background update notifications". That's
a special kind of notification that isn't mentioned by name in that
doc, but is discussed in a section of a different doc, on creating
remote notification payloads:
  https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CreatingtheNotificationPayload.html

On my iPhone 13 Pro running iOS 16.1, using breakpoint debugging in
Xcode, I don't see the method called when I receive a notification
from a Zulip server. However, if I have my dev server send
`content-available: 1` in the APNs payload (making it a "background
update notification"; see doc linked just above), then I *do* see
the method called!

I don't know any other way to interpret the qualifier in the
method's doc. My experiment was prompted by this Apple forum thread:
  https://developer.apple.com/forums/thread/128794
It seems like the doc should say more explicitly what kind of
notifications will trigger the call.

Anyway, we don't currently need to be told at all when a
notification is received, whether it's this special kind or not.
What we care about is the user's *response* to a notification: when
they tap it, we want to bring the user to the relevant conversation
in the app.

From reading code in @react-native-community/push-notification-ios
and from some experiments, this UIApplication method is the only
thing that would ever cause our `listenIOS('notification', …)`
callback to fire. So, remove that too.

…And since we were expecting that JavaScript code to handle the
user's notification *response* by navigating to a conversation, we
note that that feature must've been broken for a while. Filed just
now as issue #5679. It doesn't help that the doc for
@react-native-community/push-notification-ios incorrectly identifies
'notification' as the event carrying the user's response:
  https://github.com/react-native-push-notification/ios#how-to-determine-push-notification-user-click
…Anyway, we have a planned fix for #5679, coming next. Thankfully it
involves using less of that library, not more.

Not marking NFC because, especially with how unhelpful that Apple
doc is, I guess it's possible that the system *was* calling our
method override even without `content-available: 1` in the APNs
payloads. If so, this will be a bugfix: in those cases, before this
commit, the app would navigate to a notification's conversation
without being prompted by the user tapping on the notification.
Searching the tracker, the symptom in issue #4763 matches that
description ("[ios] Opening app from recents screen can reopen
conversation from previous notification"), but in a quick test just
now I wasn't able to reproduce that issue on current `main`, and
it's time to move on to other work.

Author: chrisbobbe

ios/ZulipMobile/AppDelegate.mm

@@ -114,13 +114,6 @@ - (void)application:(UIApplication *)application didFailToRegisterForRemoteNotif
   [RNCPushNotificationIOS didFailToRegisterForRemoteNotificationsWithError:error];
 }
 
-// Required for the notification event. You must call the completion handler after handling the remote notification.
-- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
-                                                       fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
-{
-  [RNCPushNotificationIOS didReceiveRemoteNotification:userInfo fetchCompletionHandler:completionHandler];
-}
-
 // Required for localNotification event
 - (void)userNotificationCenter:(UNUserNotificationCenter *)center
 didReceiveNotificationResponse:(UNNotificationResponse *)response

src/notification/NotificationListener.js

@@ -8,7 +8,6 @@ import type { GlobalDispatch } from '../types';
 import { androidGetToken, handleDeviceToken } from './notifTokens';
 import type { Notification } from './types';
 import * as logging from '../utils/logging';
-import { fromPushNotificationIOS } from './extract';
 import { narrowToNotification } from './notifOpen';
 
 /**
@@ -92,13 +91,6 @@ export default class NotificationListener {
       this.listenAndroid('notificationOpened', this.handleNotificationOpen);
       this.listenAndroid('remoteNotificationsRegistered', this.handleDeviceToken);
     } else {
-      this.listenIOS('notification', (notification: PushNotificationIOS) => {
-        const dataFromAPNs = fromPushNotificationIOS(notification);
-        if (!dataFromAPNs) {
-          return;
-        }
-        this.handleNotificationOpen(dataFromAPNs);
-      });
       this.listenIOS('register', this.handleDeviceToken);
       this.listenIOS('registrationError', this.handleIOSRegistrationFailure);
     }