Add new constant for PATCH method

Author: nuzil

app/code/Magento/Webapi/Model/Rest/Config.php

@@ -21,6 +21,7 @@ class Config
     const HTTP_METHOD_DELETE = 'DELETE';
     const HTTP_METHOD_PUT = 'PUT';
     const HTTP_METHOD_POST = 'POST';
+    const HTTP_METHOD_PATCH = 'PATCH';
     /**#@-*/
 
     /**#@+

app/code/Magento/WebapiAsync/Model/ServiceConfig/Converter.php

@@ -28,7 +28,7 @@ class Converter implements \Magento\Framework\Config\ConverterInterface
         \Magento\Webapi\Model\Rest\Config::HTTP_METHOD_POST,
         \Magento\Webapi\Model\Rest\Config::HTTP_METHOD_PUT,
         \Magento\Webapi\Model\Rest\Config::HTTP_METHOD_DELETE,
-        'PATCH',
+        \Magento\Webapi\Model\Rest\Config::HTTP_METHOD_PATCH
     ];
 
     /**