Cancel a signature request

curl -X POST https://api.craftkit.dev/v1/signatures/$SIGNATURE_ID/cancel \
  -H "Authorization: Bearer $CRAFTKIT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "reason": "Customer changed the terms" }'

{
  "id": "0193c2c3-2222-7aaa-8bbb-000000000002",
  "renderId": "0193c2c3-1111-7aaa-8bbb-000000000001",
  "name": "Charter handover — BK-12345",
  "status": "cancelled",
  "recipients": [],
  "expirationHours": 168,
  "signedDownloadUrl": null,
  "certificateUrl": null,
  "errorMessage": "Customer changed the terms",
  "createdAt": "2026-06-05T10:00:00.000Z",
  "completedAt": null
}