If the user modify or translate the name of the product "Gift Coupon" the system will be no more able to find it.
So, I:
1) Create a field in the sale parameters page (related to a res.company field to be stored) to select the product use in sale order line
2) Use this parameter in the controller
3) Create a migration method for existing database with this module (so just pull the module version on the customer server, restart the server and update the module)