Events retention policy

**Is your feature request related to a problem? Please describe.**
I'm finding that I'm using 30GB+ of space for my database assigned to Authentik. This appear to be mostly for events which is fine, it's good to have a long history of event logging just in case.

**Describe the solution you'd like**
I'm wondering if it'd be possible, if a default doesn't exist, to set up a retention policy so that I don't have to manually clear down event logging data in the DB. This would prevent me from having to bump up my Authentik Database PVC size every few weeks as it approaches capacity.

**Describe alternatives you've considered**
At the moment, I'm having to run a database task where it deletes any event data older than 90 days (as this is the retention period I wanted for my system).

**Additional context**
Add any other context or screenshots about the feature request here.