feat(core): update storage outputs class for multi-bucket support

packages/amplify_core/doc/lib/auth.dart

@@ -110,13 +110,13 @@ Future<void> _handleSignInResult(SignInResult result) async {
     // #enddocregion handle-signin, handle-confirm-signin-sms, handle-confirm-signin-new-password, handle-confirm-signin-custom-challenge, handle-confirm-signin-reset-password, handle-confirm-signin-confirm-signup, handle-confirm-signin-done, handle-confirm-signin-mfa-selection, handle-confirm-signin-totp-setup, handle-confirm-signin-totp-code
     // #docregion handle-confirm-signin-mfa-selection
     case AuthSignInStep.continueSignInWithMfaSelection:
-      final allowedMfaTypes = result.nextStep.allowedMfaTypes!;
+      final allowedMfaTypes = result.nextStep.allowedMfaTypes;
       final selection = await _promptUserPreference(allowedMfaTypes);
       return _handleMfaSelection(selection);
     // #enddocregion handle-confirm-signin-mfa-selection
     // #docregion handle-confirm-signin-totp-setup
     case AuthSignInStep.continueSignInWithTotpSetup:
-      final totpSetupDetails = result.nextStep.totpSetupDetails!;
+      final totpSetupDetails = result.nextStep.totpSetupDetails;
       final setupUri = totpSetupDetails.getSetupUri(appName: 'MyApp');
       safePrint('Open URI to complete setup: $setupUri');
     // #enddocregion handle-confirm-signin-totp-setup
@@ -255,7 +255,7 @@ Future<void> signOutGlobally() async {
   if (result is CognitoCompleteSignOut) {
     safePrint('Sign out completed successfully');
   } else if (result is CognitoPartialSignOut) {
-    final globalSignOutException = result.globalSignOutException!;
+    final globalSignOutException = result.globalSignOutException;
     final accessToken = globalSignOutException.accessToken;
     // Retry the global sign out using the access token, if desired
     // ...

packages/amplify_core/lib/src/config/amplify_outputs/storage/bucket_output.dart

@@ -0,0 +1,37 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'package:amplify_core/amplify_core.dart';
+
+part 'bucket_output.g.dart';
+
+@zAmplifyOutputsSerializable
+class BucketOutput 
+    with AWSEquatable<BucketOutput>, AWSSerializable, AWSDebuggable{
+
+  const BucketOutput({required this.name, required this.bucketName, required this.awsRegion});
+
+  factory BucketOutput.fromJson(Map<String, Object?> json) =>
+      _$BucketOutputFromJson(json);
+
+  final String name;
+
+  final String bucketName;
+
+  final String awsRegion;
+
+  @override
+  List<Object?> get props => [
+        name,
+        bucketName,
+        awsRegion,
+      ];
+
+  @override
+  String get runtimeTypeName => 'BucketOutput';
+
+  @override
+  Object? toJson() {
+    return _$BucketOutputToJson(this);
+  }
+}

packages/amplify_core/lib/src/config/amplify_outputs/storage/storage_outputs.dart

@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 import 'package:amplify_core/amplify_core.dart';
-import 'package:amplify_core/src/config/amplify_outputs/storage/storage_output_bucket.dart';
+import 'package:amplify_core/src/config/amplify_outputs/storage/bucket_output.dart';
 
 part 'storage_outputs.g.dart';
 
@@ -26,7 +26,7 @@ class StorageOutputs
   final String bucketName;
 
   /// The list of buckets if there are multiple buckets for the project
-  final List<StorageOutputBucket>? buckets;
+  final List<BucketOutput>? buckets;
 
   @override
   List<Object?> get props => [awsRegion, bucketName, buckets];