Record an audit event for a change made in the console

Ingest for the few mutations that happen in the customer console's own database, so the control plane never sees them. Everything the control plane changes itself is recorded by its own handler and is not accepted here. The organization, actor, address and time are derived on the server; the body names only the action, an optional target and a small before and after summary. Requires an API key whose role may manage identity settings (admin or owner); a widget JWT is refused with 403, and a 503 means the audit log is not configured on the deployment.