Support for cognito endpoint

Added ability to add equivalent of AWS_ENDPOINT_URL to cognito user pool requests. This is done by adding `CognitoUserPool > Default > Endpoint` to the configuration. The endpoint must contain the pool ID like `http://localhost:4556/us-east-1_pool_id`.

Author: jboshoven-emporia

packages/amplify_core/lib/src/config/amplify_outputs/auth/auth_outputs.dart

@@ -20,6 +20,7 @@ class AuthOutputs
     required this.awsRegion,
     this.userPoolId,
     this.userPoolClientId,
+    this.userPoolEndpoint,
     this.appClientSecret,
     this.identityPoolId,
     this.passwordPolicy,
@@ -44,6 +45,9 @@ class AuthOutputs
   /// The Cognito User Pool Client ID.
   final String? userPoolClientId;
 
+  /// The Cognito User Pool Endpoint.
+  final String? userPoolEndpoint; //Gen 1 only
+
   /// A fixed string that must be used in all API requests to the app client
   /// if the the app client has one configured.
   ///
@@ -84,6 +88,7 @@ class AuthOutputs
     awsRegion,
     userPoolId,
     userPoolClientId,
+    userPoolEndpoint,
     identityPoolId,
     oauth,
     standardRequiredAttributes,

packages/amplify_core/lib/src/config/amplify_outputs/auth/auth_outputs.g.dart

@@ -137,6 +137,7 @@ class AuthConfig extends AmplifyPluginConfigMap {
       awsRegion: region,
       userPoolId: userPool?.poolId,
       userPoolClientId: userPool?.appClientId,
+      userPoolEndpoint: userPool?.endpoint,
       appClientSecret: userPool?.appClientSecret,
       identityPoolId: identityPool?.poolId,
       passwordPolicy: passwordPolicy,

packages/amplify_core/lib/src/config/auth/auth_config.dart

@@ -78,6 +78,7 @@ final class ConfigurationStateMachine
         region: authOutputs.awsRegion,
         credentialsProvider: _credentialsProvider,
         dependencyManager: this,
+        endpoint: authOutputs.userPoolEndpoint,
       ),
     );