invora.simple.invoices.v1.SimpleRegulationArtifact

A reference to a file produced by the tax authority during submission
(the signed XML, the QR-code image, the clearance response, etc.).
The bytes are NOT inlined here — download them with the service's
GetArtifact RPC using (document key, id). This keeps read responses
small and lets clients fetch only the artifacts they need.

{
    "id": "string",
    "contentType": "string",
    "sha256": "string",
    "sizeBytes": "string"
}