[mdx] [gn3-jra3-t2] Querying a list of Identity Providers from the Metadata Aggregator

[Scott Cantor]

> > I believe one of the things we should discuss in tomorrows VC is the
> possibility of getting rid of large chunks of signed XML once for all? If
> so, the missing part would be to let the the discovery service get all the
> data it needs; and I wrote some lines about that here:
> >
> > 	https://rnd.feide.no/content/querying-list-identity-providers-
> metadata-aggregator
> >
> > Comments expected and appreciated!

I'm inclined to say it should be a local problem to transform metadata into
JSON if that's deemed necessary (a necessity I'm still not a fan of).
 
Alternatively, if the metadata itself is somehow too complex, I'd advocate a
different format, perhaps XRD, to reduce the information required, and
simplify the transformation. 

-- Scott