I'm trying to add gift card and promo code functionality for invoices for custom products. I am able to see a gift and promo code box in E-Commerce checkout, but it does not appear on Invoice payment pages for some reason. The current temporary workaround I have is to set up a separate non-Odoo form embedded on a page which takes payment by gift card and then sends data through API to reduce the value of said invoice by the amount of the gift card. 

Additionally, is it possible to set up a quick pay invoice page? It would be much nicer to allow customers to pay invoice by number as well.