curl --request POST \
  --url https://api-testnet.context.markets/v2/orders/cancel \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "trader": "0x1111111111111111111111111111111111111111",
  "nonce": "0xabc123",
  "signature": "0xabc123"
}
'

{
  "success": true,
  "alreadyCancelled": true
}