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

Fixes #407

Author: AhmedTareek

Diff for: 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)

Diff for: 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:

Diff for: 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;