notif: Use live value for app ID on registering APNs token

`await ZulipBinding.instance.packageInfo` was added to get the
packageName, making `registerToken` take longer to complete.
Previously, in "token initially unknown" test in the
UpdateMachine.registerNotificationToken `start()` and
`_registerNotificationToken()` finished in sync with the test’s
expectations. Now, a delay is added to ensure that the listener
callback `_registerNotificationToken()` finishes its async work
before continuing the test.

Fixes #407

Author: AhmedTareek

lib/model/binding.dart

@@ -303,10 +303,12 @@ class LinuxDeviceInfo implements BaseDeviceInfo {
 class PackageInfo {
   final String version;
   final String buildNumber;
+  final String packageName;
 
   const PackageInfo({
     required this.version,
     required this.buildNumber,
+    required this.packageName
   });
 }
 
@@ -411,6 +413,7 @@ class LiveZulipBinding extends ZulipBinding {
       _syncPackageInfo = PackageInfo(
         version: info.version,
         buildNumber: info.buildNumber,
+        packageName: info.packageName
       );
     } catch (e, st) {
       assert(debugLog('Failed to prefetch package info: $e\n$st')); // TODO(log)

lib/notifications/receive.dart

@@ -149,9 +149,12 @@ class NotificationService {
         await addFcmToken(connection, token: token);
 
       case TargetPlatform.iOS:
-        const appBundleId = 'com.zulip.flutter'; // TODO(#407) find actual value live
-        await addApnsToken(connection, token: token, appid: appBundleId);
-
+        final packageInfo = await ZulipBinding.instance.packageInfo;
+        if (packageInfo == null) {
+          assert(debugLog('missing packageInfo')); // TODO(log)
+        }
+        await addApnsToken(connection, token: token,
+            appid: packageInfo?.packageName ?? 'com.zulip.flutter');
       case TargetPlatform.linux:
       case TargetPlatform.macOS:
       case TargetPlatform.windows:

test/api/core_test.dart

@@ -460,7 +460,7 @@ void main() {
       });
     }
 
-    const packageInfo = PackageInfo(version: '0.0.1', buildNumber: '1');
+    const packageInfo = PackageInfo(version: '0.0.1', buildNumber: '1', packageName: 'com.zulip.flutter');
 
     const testCases = [
       ('ZulipFlutter/0.0.1+1 (Android 14)',             AndroidDeviceInfo(release: '14', sdkInt: 34),                      ),

test/model/binding.dart

@@ -231,7 +231,8 @@ class TestZulipBinding extends ZulipBinding {
 
   /// The value that `ZulipBinding.instance.packageInfo` should return.
   PackageInfo packageInfoResult = _defaultPackageInfo;
-  static const _defaultPackageInfo = PackageInfo(version: '0.0.1', buildNumber: '1');
+  static const _defaultPackageInfo = PackageInfo(version: '0.0.1',
+      buildNumber: '1', packageName: 'com.zulip.flutter');
 
   void _resetPackageInfo() {
     packageInfoResult = _defaultPackageInfo;

test/model/store_test.dart

@@ -1177,6 +1177,9 @@ void main() {
       // When the token later appears, send it.
       connection.prepare(json: {});
       await startFuture;
+      // This delay is needed to allow the listener callback to `store._registerNotificationToken()`
+      // that occurs as a side effect of `startFuture` setting the token value to complete.
+      await Future<void>.delayed(Duration.zero);
       if (defaultTargetPlatform == TargetPlatform.android) {
         checkLastRequestFcm(token: '012abc');
       } else {