idp reports back if user has 2fa
the idp returns a different authncontext depending on the user having 2fa enabled. by default it returns
urn:oasis:names:tc:SAML:2.0:ac:classes:Password
with 2fa
urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordWith2FA
there seems to be no agreed upon standard what to return and also no sensible default option.