Earlier quoted context omitted.
Cool. I never used Shopify. Didn't know you can use them to sell digital goods. Do you have to integrate your own payment or do they handle it all for you? Do they collect the money from users and then send it to you once per month? Do they handle the tricky parts like dealing with VAT per country?
I basically use the API to create a checkout specific to the user's order, then listen to the webhook to fulfill the credits. Gateways are Shopify and PayPal. Shopify payments are in my bank account in a couple of days.
Do you need a PayPal account and dabble with their API to set up this type of solution?
Or is a Shopfiy account enough?