Pass custom parameter to OrderItemAddCmd in FEB 8

In FEB 8, They are calling all the controller command as rest. So If you want to pass any custom parameter to the OrderItemAddCmd, we don't need to customize the order facade client. In the previous version we had done that way.

Please follow the steps:

1. The Request parameter mapping for all the rest commands is in this template file "\Stores\WebContent\WEB-INF\config\com.ibm.commerce.order-fep\rest-template-config.xml"

 So please add your custom entry as "x_warrenty."

2.Pass the custom param with the request "warrenty".

3.Then extend the OrderItemAddCmd then do the bussiness logic.