First, I wanted to integrate a button in cart extension but it just didn’t work. I couldn’t make a pop-up QR and other UI functionality. So read somewhere that it does not allow a lot of modification. So, now I am trying it with theme extension, with all recommended settings and I am getting “No permission/access” using webhooks. I have already applied everything for test store settings.
Idea is "once user click on my button XYZ(like add discount), the cart price value should change, then user goes to checkout, should see final price with discount, and send the receipt data to the firebase so that I can show it in my app to the user instantly.
Should I use shopify graphql API, webhooks, admin API or something else? And how? What am I missing in webhooks?