Idempotency-Key header on POST /v1/kennet/twins: any unique string of 1 to 255 printable ASCII characters, such as a UUID. If you retry with the same key, you never start a second run.
The same request means the same file name, the same file bytes, the same
key and the same confidential list.
A request that failed with any error holds no key, so you can retry it with the same key. After 24 hours a key is forgotten and can be used again.
Keys are kept per organization and per mode. A test key and a live key never share a key.