BlockHistoryScrubExecuteResponse

What the execute door's act did: a completion and a refusal are different answers, so the
response is a tagged enum. A refusal here is an operator-facing one (charter_resource,
already_erased); a caller who is not a system admin never reaches the act.

{ "cancelled_ingest": true, "event_id": "a7a26ff2-e851-45b6-9634-d595f45458b7", "request_reference": "befa7ed4-201c-4983-ac08-b6179835da7c", "status": "completed", "targets": [ { "outcome": "string", "target": "string" } ] }