* Copy audit logs impl from old branch and clean up
I suck at using git, so I'm gonna use brute force.
* Remove unnecessary TODOs
Category channels do not provide any new information, and the other
I forgot to remove beforehand
* Add invite update data, clean up after feedback
* Remove TODOs, add WebhookType enum for future use
WebhookType is a future-use type, as currently audit logs are the only
thing which may return it.
