AZ711: The audit trail can't be changed

authz.audit only grows: rows can't be updated or deleted, even by the owner, except by authz.trim_audit(interval), which removes what is older than the interval.

Reported to the app, by the authz.* functions and the policy's rules: the code is in the error's HINT (rowfence help AZ709), and the SDKs' errors carry it as code.