Expose parameter passed to exceptions

src/Exception/InvalidGrantException.php

@@ -32,6 +32,7 @@ class InvalidGrantException extends OAuthException
 
     public function __construct($parameter)
     {
+        $this->parameter = parameter;
         parent::__construct(
             sprintf(
                 'The provided authorization grant is invalid, expired, revoked, does not match the redirection URI used in the authorization request, or was issued to another client. Check the "%s" parameter.',