Tender and close a Simphony STS Gen2 check via the check round endpoint

Steps

1. Look up a valid tenderId via GET /api/v1/tenders/collection before attempting to tender
2. POST to /api/v1/checks/{checkRef}/round with a tenders array containing a CheckTenderItem
3. Set the tender total to zero to auto-tender and close the check for the full remaining balance, or to a specific amount for a partial payment
4. Only include chargedTipTotal when over-tendering the full remaining balance plus tip — it is not supported alongside partial payment
5. Avoid sending paymentData/SPI fields unless you are an Oracle-vetted payment partner; otherwise reference a real tender of type 'payment' from the tenders collection
6. Confirm the check's header.status flips from open to closed once paid in full, and stop sending further modifications since closed checks cannot be changed