post
https://api.sandbox.hint.com/api/provider/customer_invoices//payments
Payments can be created only against an issued, sent, retrying, or bad_debt invoice;
any other status fails with 422 Invoice is not payable. An invoice can not be overpaid:
an amount_in_cents above the invoice's due_in_cents fails with
422 Amount is greater than the amount due on the invoice, and a new payment while an
earlier one is still in flight fails with 422 Invoice has a pending payment or
422 Invoice has an unattempted payment.
The returned amount_in_cents is the gross amount attempted on the payment method and may
include processing fees passed through to the patient, so it can exceed the invoice total.
Use the invoice's paid_in_cents for the amount applied to the invoice.

