MFA flow: which authns are reused

[Jim Fox]

>> How can I get the username in that case?
>
> The Duo flow (and probably anything in the future) uses a strategy function to get the username, net.shibboleth.idp.session.context.navigate.CanonicalUsernameLookupStrategy
>

Thanks,  I'll look there.

And there's still time to rename this the MultiFlowAuthn (MFA) flow.  More 
fitting, I think.

Jim