Add authUser to req when performing an API auth
Add authUser to req when performing an API auth

This will make (possibly) make it simpler to use the authenticated API
endpoints since the auth token should have the user email embedded in
it. Endpoints that take advantage of `req.authUser` should no longer
have to ask for the user email address.

kayaelle/msol-badger,kayaelle/msol-badger,bdgio/msol-site,mozilla/openbadger,bdgio/msol-site,kayaelle/msol-badger,bdgio/msol-site,mozilla/openbadger