Update Payment

Update an existing payment record by its own id — no invoice or bill id is required in the path.

Supports partial updates of amount, paymentMethod, paymentDate, notes, and paymentReference — the same fields the Coperniq UI exposes when editing a logged payment.

If the payment is external (processed by Stripe), only notes may be updated; any other field returns a 400.

Updating amount may fail with a 400 if the new total would exceed the parent invoice/bill's outstanding balance. The parent document's amountPaid/status are recalculated automatically.