Selecting Duo integration during MFA script

[Cantor, Scott]

> A good suggestion, but there is a Duo API call that needs to
> happen in the MFA script to decide whether to invoke the
> Duo auth in the first place that I would prefer not to have to
> duplicate within the integration strategy. . .

Stashing something is fine, the ScratchContext class is the most advisable place/way to do that. We don't use it (I think that's basically a hard and fast rule we have, but I'll review) so anything you do with it should be entirely private.

-- Scott