fixing exception with authenticateUser

lib/sig_v4.dart

@@ -9,7 +9,7 @@ const _x_amz_date = 'x-amz-date';
 const _x_amz_security_token = 'x-amz-security-token';
 const _host = 'host';
 const _authorization = 'Authorization';
-const _default_content_type = 'application/json';
+const _default_content_type = 'application/json; charset=utf-8';
 const _default_accept_type = 'application/json';
 
 class AwsSigV4Client {

lib/src/cognito_credentials.dart

@@ -25,13 +25,13 @@ class CognitoCredentials {
   }
 
   /// Get AWS Credentials for authenticated user
-  Future<void> getAwsCredentials(token) async {
+  Future<void> getAwsCredentials(token, [String authenticator]) async {
     if (expireTime == null ||
         new DateTime.now().millisecondsSinceEpoch > expireTime - 60000) {
       final identityId = new CognitoIdentityId(_identityPoolId, _pool);
-      final identityIdId = await identityId.getIdentityId(token);
+      final identityIdId = await identityId.getIdentityId(token, authenticator);
 
-      final authenticator = 'cognito-idp.$_region.amazonaws.com/$_userPoolId';
+      authenticator ??= 'cognito-idp.$_region.amazonaws.com/$_userPoolId';
       final Map<String, String> loginParam = {
         authenticator: token,
       };

lib/src/cognito_identity_id.dart

@@ -18,14 +18,14 @@ class CognitoIdentityId {
   }
 
   /// Get AWS Identity Id for authenticated user
-  Future<String> getIdentityId(token) async {
+  Future<String> getIdentityId(token, [String authenticator]) async {
     final identityIdKey = 'aws.cognito.identity-id.$_identityPoolId';
     String identityId = await _pool.storage.getItem(identityIdKey);
     if (identityId != null) {
       this.identityId = identityId;
       return identityId;
     }
-    final authenticator = 'cognito-idp.$_region.amazonaws.com/$_userPoolId';
+    authenticator ??= 'cognito-idp.$_region.amazonaws.com/$_userPoolId';
     final Map<String, String> loginParam = {
       authenticator: token,
     };

lib/src/cognito_user.dart

@@ -142,7 +142,7 @@ class CognitoUser {
         ['DeviceKey'];
     await cacheDeviceKeyAndPassword();
 
-    if (dataConfirm['UserConfirmationNecessary'] == true) {
+    if (dataConfirm['UserConfirmationNecessary'] == true && !_signInUserSession.isValid()) {
       throw new CognitoUserConfirmationNecessaryException(
           signInUserSession: _signInUserSession);
     }