WIP: ExMonobank.MerchantAPI

[sveredyuk]

@romkor I Just started extracting my code into ExMonobank.MerchantAPI. Work in progress, but we can start the discussion right now )

[romkor]

Good job!
I have mixed fillings about Invoice module name, not clear that it is mutation DTO.
But I can live with it.
WDYT?

[romkor]

Not a big deal, just typo in file name:
cancel_invoice_failure_with_inbvalid_id.json
should be:
cancel_invoice_failure_with_invalid_id.json

[sveredyuk]

Good job! I have mixed feelings about Invoice module name, not clear that it is mutation DTO. But I can live with it. WDYT?

Me too. We need clear separate request structs and response structs. I'm just bad at naming :)
ExMonobank.Invoice - request struct
ExMonobank.InvoiceInfo - response structs

{:ok, invoice_info} =
  %{amount: 100}
  |> ExMonobank.Invoice.new()
  |> MerchantAPI.create_invoice()

I am open to any suggestions.