<tl;dr> how do we go about building a custom payment channel/plugin that can be used for our client's existing loyalty programme redemptions?
We have built a headless shopify store (one in flutter and one using Lit-element - both augmented with a firebase back-end) for a client that has a well established loyalty programme (bricks and mortar included); We have interfaced to their loyalty programme API to earn and redeem points; the latter by dynamically creating single-use, single-customer discount codes to the value of the redemption. We even figured out that we can allow customers to also pay for shipping (below free level) using redemption points by adding a fictitious 100kg product called Redemption Shipping priced at the same price as standard shipping which triggers a free shipping rule.
However, since the points are actual tender/money I would prefer we build a custom payment API to work/integrate with our shopify stores - this will also allow customers to user discount codes and discount vouchers (without us having to consolidated them into a single discount).
Should we be using the Payment API/SDK for this? I looked the other day and it seems to be on ice prior to a new approach/SDK being released -was I looking in the right place?