Prevent oauth secrets from being exposed in logs via override messages

[wo2wz]

oauth secret options like OAUTH_OIDC_CLIENT_SECRET should be censored or suppressed in the environment variable override logs under normal circumstances, since with tools like systemd's journalctl it is possible to view them plainly, unprivileged.

[diced]

this isn't something zipline needs to do, but rather your log viewing thing should be able to redact certain stuff, as well as making them unable to be viewed without the correct privileges.