Dynamic payment processors in addition to Stripe Connect

[kpalang]

I am in need of paid bookings functionality, but am historically tied to a local payment gateway provider. Their flow is the same redirect flow with a callback as Stripe Connect.

I think a good first approach would be to put payment processing behind what's called an interface in Java world (forgive me for my lack of Go knowledge, I'm a Java dev) and make each gw provider extend that interface. I don't think a fully fledged plugin system dynamic (un-)loading is required or even reasonable. I'd be happy with the implementing classes living directly in the source code, as most integrations would be nearly write-and-forget type endeavors, anyway.

Unstructured thoughts:

• I'd love if writing the integration took as few files as possible, in contrast to the steaming heap that is cal.diy;
• There might be need to keep track of the gw implementations in the db as a booking entity needs to keep track of which gateway it should use;
• A gateway should be selectable per event-type, but configured by admin site-wide;