Add option to Enforce use of MFA

Similar to other application e.g. in Github (Orgs) it would be great to enforce MFA for all accounts in Homeassistant.
As this can only be setup after login it may need an additional MFA enable screen before being able to use the account.

Usecase is that for a internet reachable instance i`d like to make MFA mandatory for all users to have strong security for all accounts in homeassistant.

Would this make sense for others too ? :slight_smile: