POST /v1/cancel1{ "maker": "0x1111…", "nonce": 43, "orderNonce": 42, "signature": "0x…" }
body makeraddressrequiredbody nonceuint64requiredbody orderNonceuint64requiredbody signaturestringrequiredCancel, by the maker or a key it registered.1{ "status": "cancelled" }
status is cancelled, unknown (no answer in time; check the order), or the
engine's refusal code, such as ORDER_NONCE_NOT_FOUND when the order is not
resting. An engine refusal is still a 200.