feat(multi-payment-methods): add payment method selection to invoices and payment requests

[aquinofb]

Summary

Add PaymentMethodReference schema enabling users to specify payment method (provider or manual) when creating invoices, retrying payments, and creating payment requests. Also adds payment_method_id to Payment response object.

• Create PaymentMethodReference.yaml schema
• Add payment_method_id to PaymentObject response
• Add optional request body to POST /invoices/{id}/retry_payment
• Add payment_method to invoice one-off creation input
• Add payment_method to payment request creation input

[mariohd]

I can't find the reference for this param here

[aquinofb]

Great catch!

That's the same case as V1::PaymentSerializer, where it is available in Gql, but not in the controller.

In the ReqCreateInput, we have it in the Gql (GitHub), but it's not available in the controller you linked.

[mariohd]

We have to ask Mike about it, sometimes the fields are hidden in the API but available through Front (GQL).

I don't think it's the case here.
cc: @lovrocolic

[mariohd]

We also need to add this, not sure in this PR or other

invoice_custom_section: [
  :skip_invoice_custom_sections,
  {invoice_custom_section_codes: []}
]

[aquinofb]

I couldn't see this anywhere else. Probably we'd need to add to many places at once? Shall we leave it to another pull request? If not, I'm happy to include in this one

[mariohd]

I prefer to have this in other PR.

it's not entirely related to multiple payment methods, but it has inside this feature (Dive In Part 2).
It's a completely new feature and deserves another PR.

[mariohd]

Looks good, just one comment and a question