curl -X POST 'https://developers.flouci.com/api/v2/cancel_payment' \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer <PUBLIC_KEY>:<PRIVATE_KEY>' \
  -d '{
    "payment_id": "a1b2c3d4-e5f6-7890-1234-567890abcdef"
  }'

{
  "result": {
    "payment_id": "a1b2c3d4-e5f6-7890-1234-567890abcdef",
    "status": "cancelled",
    "cancelled_at": "2025-01-15T10:30:00Z"
  },
  "status": "success"
}

{
  "status": "error",
  "message": "Pre-auth payment cannot be cancelled",
  "code": "CANCELLATION_FAILED"
}