mod_http_oauth2: Don't issue client_secret when not using authentication This is pretty much only for implicit flow, which is considered insecure anyway, so this is of limited value. If we delete all the implicit flow code, this could be reverted.

---
summary: Store registration events in the audit log
rockspec:
  dependencies:
  - mod_audit
...

This module stores successful user registrations in the audit log provided by
`mod_audit`.