Flutter iOS FCM 연동

1. Apple Push Notification 등록
2. Firebase 연동
3. Info.plist 파일에 추가

<key>FirebaseAppDelegateProxyEnabled</key>
<string>0</string>
<key>FirebaseScreenReportingEnabled</key>
<true/>

4. AppDelegate.swift에 추가

 override func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
       Messaging.messaging().apnsToken = deviceToken
       super.application(application, didRegisterForRemoteNotificationsWithDeviceToken: deviceToken)
     }

5. Firebase Messaging listener 부여할 때 권한주기

void _requestIOSPermission() {
    _firebaseMessaging.requestNotificationPermissions(
        IosNotificationSettings(sound: true, badge: true, alert: true)
    );
    _firebaseMessaging.onIosSettingsRegistered
        .listen((IosNotificationSettings settings)
    {
      print("Settings registered: $settings");
    });
  }

6. Xcode > Runner > TARGETS > Signin & Capabilities > + Capability에서 기능 추가하기

• Background Modes > Remote notifications
• Push Notifications