LG-766 Require MFA after 12 hours for IAL2 and AAL2

[jmhooper]

Why: The NIST standards require that MFA be expired after 12 hours.
This commit checks the MFA status during the handoff to the SP and
requires the user to re-auth if their device was remembered and their
cookie is older than 12 hours.

How: When a user is MFAed by remember device, flag the session.
Before redirecting to a service provider, check or whether remember
device was used, and if so, if it has expired for the current sp's
configuration. If it has, redirect to the 2FA controller. Also, it is
necessary to prevent the 2FA controller from redirecting if the user is
logged in when the remember device cookie is invalid per the current
SP's configuration.

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[jmhooper]

This was changed since now handle_valid_otp removes the mfa_device_remembered flag.

[konklone]

What does the re-auth check look like? Would you mind sharing a screenshot?

[jmhooper]

Let me get one real quick, but right now it just looks like the regular sign in flow if you start from an SP.

If you start from secure.login.gov and sign in and then go to an SP while still authed, it looks like the regular sign in flow w/o the username / password.

[jmhooper]

I have videos, but they're too large to share on GH. Let me see if I can share them in slack.