feat(auth, apple): Game Center sign-in support

docs/auth/federated-auth.md

@@ -244,6 +244,24 @@ Future<UserCredential> signInWithApple() async {
 }
 ```
 
+## Apple Game Center (Apple only) {:#games}
+
+Ensure the "Game Center" sign-in provider is enabled on the [Firebase Console](https://console.firebase.google.com/project/_/authentication/providers).
+Follow these instructions for [Game Center Firebase project set-up](https://firebase.google.com/docs/auth/ios/game-center#before_you_begin).
+
+You will need to login with Game Center before a Firebase Game Center credential can be issued and logged in via Firebase. [Here are some instructions](https://firebase.google.com/docs/auth/ios/game-center#integrate_game_center_sign-in_into_your_game)
+on how that can be achieved.
+
+* {iOS+}
+
+```dart
+Future<void> _signInWithGameCenter() async {
+  final credential = GameCenterAuthProvider.credential();
+  await FirebaseAuth.instance
+      .signInWithCredential(credential);
+}
+```
+
 ## Microsoft
 
 * {iOS+}

packages/firebase_auth/firebase_auth/example/ios/Runner.xcodeproj/project.pbxproj

@@ -295,6 +295,7 @@
 				"${BUILT_PRODUCTS_DIR}/flutter_facebook_auth/flutter_facebook_auth.framework",
 				"${BUILT_PRODUCTS_DIR}/flutter_secure_storage/flutter_secure_storage.framework",
 				"${BUILT_PRODUCTS_DIR}/nanopb/nanopb.framework",
+				"${BUILT_PRODUCTS_DIR}/path_provider_foundation/path_provider_foundation.framework",
 				"${BUILT_PRODUCTS_DIR}/shared_preferences_foundation/shared_preferences_foundation.framework",
 				"${BUILT_PRODUCTS_DIR}/url_launcher_ios/url_launcher_ios.framework",
 				"${PODS_XCFRAMEWORKS_BUILD_DIR}/FBAEMKit/FBAEMKit.framework/FBAEMKit",
@@ -321,6 +322,7 @@
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/flutter_facebook_auth.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/flutter_secure_storage.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/nanopb.framework",
+				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/path_provider_foundation.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/shared_preferences_foundation.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/url_launcher_ios.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/FBAEMKit.framework",

packages/firebase_auth/firebase_auth/example/ios/Runner/Runner.entitlements

@@ -8,5 +8,7 @@
 	<array>
 		<string>Default</string>
 	</array>
+	<key>com.apple.developer.game-center</key>
+	<true/>
 </dict>
 </plist>

packages/firebase_auth/firebase_auth/lib/firebase_auth.dart

@@ -39,6 +39,8 @@ export 'package:firebase_auth_platform_interface/firebase_auth_platform_interfac
         EmailAuthCredential,
         FacebookAuthProvider,
         FacebookAuthCredential,
+        GameCenterAuthProvider,
+        GameCenterAuthCredential,
         PlayGamesAuthProvider,
         PlayGamesAuthCredential,
         GithubAuthProvider,

packages/firebase_auth/firebase_auth_platform_interface/lib/firebase_auth_platform_interface.dart

@@ -28,6 +28,7 @@ export 'src/platform_interface/platform_interface_user_credential.dart';
 export 'src/providers/apple_auth.dart';
 export 'src/providers/email_auth.dart';
 export 'src/providers/facebook_auth.dart';
+export 'src/providers/game_center_auth.dart';
 export 'src/providers/github_auth.dart';
 export 'src/providers/google_auth.dart';
 export 'src/providers/microsoft_auth.dart';

packages/firebase_auth/firebase_auth_platform_interface/lib/src/providers/game_center_auth.dart

@@ -0,0 +1,68 @@
+// Copyright 2024 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:firebase_auth_platform_interface/firebase_auth_platform_interface.dart';
+
+const _kProviderId = 'gc.apple.com';
+
+/// This class should be used to create a new Game Center credential
+/// to trigger an authentication flow on Apple platform.
+///
+/// ```dart
+/// // Requires authenticating with game center before proceeding with the below:
+/// final gameCenterCredential = GameCenterAuthProvider.credential();
+///
+/// FirebaseAuth.instance.signInWithCredential(gameCenterCredential)
+///  .then(...);
+/// ```
+class GameCenterAuthProvider extends AuthProvider {
+  /// Creates a new instance.
+  GameCenterAuthProvider() : super(_kProviderId);
+
+  /// Create a new [GameCenterAuthCredential] to be used on FlutterFire
+  /// Auth plugin only.
+  static OAuthCredential credential() {
+    return GameCenterAuthCredential._credential();
+  }
+
+  /// This corresponds to the sign-in method identifier.
+  static String get GAME_CENTER_SIGN_IN_METHOD {
+    return _kProviderId;
+  }
+
+  // ignore: public_member_api_docs
+  static String get PROVIDER_ID {
+    return _kProviderId;
+  }
+
+  Map<String, String> _parameters = {};
+
+  /// Returns the parameters for this provider instance.
+  Map<String, String> get parameters {
+    return _parameters;
+  }
+
+  /// Sets the OAuth custom parameters to pass in a Game Center OAuth request for
+  /// popup and redirect sign-in operations.
+  GameCenterAuthProvider setCustomParameters(
+    Map<String, String> customOAuthParameters,
+  ) {
+    _parameters = customOAuthParameters;
+    return this;
+  }
+}
+
+/// The auth credential returned from calling
+/// [GameCenterAuthProvider.credential].
+class GameCenterAuthCredential extends OAuthCredential {
+  GameCenterAuthCredential._()
+      : super(
+          providerId: _kProviderId,
+          signInMethod: _kProviderId,
+        );
+
+  factory GameCenterAuthCredential._credential() {
+    return GameCenterAuthCredential._();
+  }
+}