There is a call to .FeaturedWorks ("/api/v1/sets") in the app delegate as a proof-of-concept.

The basics of use are, instead of calling ArtsyProvider.request(.Whatever) as you normally would, you just call ArtsyProvider.XAppRequest(.Whatever). It'll check if the XApp token is present and hasn't expired yet, transparently fetching a new one if required, and signing all non-XApp token requests with the XApp token.

Work-in-progress because I still want to address:

• Needs tests.
• I don't like the ReactiveMoyaProvider extension instance method referencing ArtsyProvider, an instance of that class.