[mdx] [Shib-Dev] Dynamic Metadata Provider for IdP

[Scott Cantor]

> There is occasionally method to my madness.

What got lost in translation is that my dynamic plugin started as "you know
the IdP, go ask it for its metadata", and now that the template option can
muck with the entityID, it can become "you don't know the IdP, go ask third
party for metadata about an opaque string".

This raises a question though...if I'm understanding things correctly,
there's no standard tagging syntax here (yet anyway), so would an
implementation of the client need to be able to use a different URL template
for "look up by entityID" vs. "lookup by artifact source ID"?

-- Scott