TF-2756 Fix universal links on iOS

Author: lukevital

src/ios/AppDelegate+FirebasePlugin.m

@@ -290,12 +290,6 @@ - (void)application:(UIApplication *)application didFailToRegisterForRemoteNotif
     [FirebasePlugin.firebasePlugin _logError:[NSString stringWithFormat:@"didFailToRegisterForRemoteNotificationsWithError: %@", error.description]];
 }
 
-- (BOOL)application:(nonnull UIApplication *)application
-            openURL:(nonnull NSURL *)url
-            options:(nonnull NSDictionary<NSString *, id> *)options {
-  return [[GIDSignIn sharedInstance] handleURL:url];
-}
-
 - (void)userNotificationCenter:(UNUserNotificationCenter *)center openSettingsForNotification:(UNNotification *)notification
 {
     @try {

src/ios/FirebasePlugin.m

@@ -55,6 +55,12 @@ + (void) setFirestore:(FIRFirestore*) firestoreInstance{
     firestore = firestoreInstance;
 }
 
+- (void)applicationLaunchedWithUrl:(NSNotification*)notification
+{
+    NSURL* url = [notification object];
+    [[GIDSignIn sharedInstance] handleURL:url];
+}
+
 // @override abstract
 - (void)pluginInitialize {
     NSLog(@"Starting Firebase plugin");
@@ -64,6 +70,8 @@ - (void)pluginInitialize {
         preferences = [NSUserDefaults standardUserDefaults];
         googlePlist = [NSMutableDictionary dictionaryWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"GoogleService-Info" ofType:@"plist"]];
 
+        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationLaunchedWithUrl:) name:CDVPluginHandleOpenURLNotification object:nil];
+
         if([self getGooglePlistFlagWithDefaultValue:FirebaseCrashlyticsCollectionEnabled defaultValue:YES]){
             [self setPreferenceFlag:FIREBASE_CRASHLYTICS_COLLECTION_ENABLED flag:YES];
         }
@@ -81,7 +89,7 @@ - (void)pluginInitialize {
 
         // Check for permission and register for remote notifications if granted
         [self _hasPermission:^(BOOL result) {}];
-        
+
 
         authCredentials = [[NSMutableDictionary alloc] init];
         firestoreListeners = [[NSMutableDictionary alloc] init];
@@ -738,15 +746,15 @@ - (void)authenticateUserWithGoogle:(CDVInvokedUrlCommand*)command{
         [GIDSignIn.sharedInstance signInWithConfiguration:googleSignInConfig presentingViewController:self.viewController callback:^(GIDGoogleUser * _Nullable user, NSError * _Nullable error) {
           __auto_type strongSelf = weakSelf;
           if (strongSelf == nil) { return; }
-            
+
             @try{
                 CDVPluginResult* pluginResult;
                 if (error == nil) {
                     GIDAuthentication *authentication = user.authentication;
                     FIRAuthCredential *credential =
                     [FIRGoogleAuthProvider credentialWithIDToken:authentication.idToken
                                                    accessToken:authentication.accessToken];
-                    
+
                     NSNumber* key = [[FirebasePlugin firebasePlugin] saveAuthCredential:credential];
                     NSString *idToken = user.authentication.idToken;
                     NSMutableDictionary* result = [[NSMutableDictionary alloc] init];