See #3709: when an account is deleted, we can no longer easily look up who did what.

The summary in each auditlog entry starts with the username (str) of the actor, so it is possible to rescue who did what that way.

We could have a script that repairs the actor model_pk with an integer not currently used as a pk in the account table. Run once on a NAV instance that has merged the chosen solution to #3709 and the problem is gone.