Add Organizational event logging feature

This PR adds event/audit logging support for organizations.
By default this feature is disabled, since it does log a lot and adds
extra database transactions.

All events are touched except a few, since we do not support those
features (yet), like SSO for example.

This feature is tested with multiple clients and all database types.

Fixes #229

src/api/mod.rs

@@ -17,6 +17,7 @@ pub use crate::api::{
     core::routes as core_routes,
     core::two_factor::send_incomplete_2fa_notifications,
     core::{emergency_notification_reminder_job, emergency_request_timeout_job},
+    core::{event_cleanup_job, events_routes as core_events_routes},
     icons::routes as icons_routes,
     identity::routes as identity_routes,
     notifications::routes as notifications_routes,