Enhanced security options for authentik's admin interface

**Is your feature request related to a problem? Please describe.**
No

**Describe the solution you'd like**
I would like a way for users to optionally enhance security for the admin interface.

**Describe alternatives you've considered**
- Using another account as admin strictly for admin-related duties
- However this will keep me from getting notifications like new authentik-versions in the dashboard.
- Also this would be an unintuitive approach as I would have to log out of my main account and into an admin account each time I would like to do admin-actions.

**Additional context**
In my opinion the best approach would be to turn admin interface access into its own flow.
This would allow for most customizability.

As a short term solution, security could be provided by an optional variable to force 2FA-Validation to access the admin interface (preferably per session).