curl --request POST \
  --url https://api.sandbox.zafapay.com/v1/payments/{id}/refund \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "amount": 5.5,
  "reason": "お客様都合"
}
'

{
  "id": "orf_xyz789",
  "transaction_id": "tx_abc123",
  "amount": "5.50",
  "status": "succeeded",
  "psp_refund_id": "re_xxxxx",
  "refund_fee": "1.00"
}