Export types auth/0 and priv_set/0 for a better analyzing of backend
implementations
Allow authorization with a previously authenticated resource owner

This adds a new function `authorize_resource_owner/3` for establishing
authorization where the resource owner has already been authenticated.
Useful in the case where the Authentication Server is separate to the
Authorization Server.
Merge pull request #35 from danielwhite/authorize-resource-owner

Allow authorization with a previously authenticated resource owner
Merge pull request #36 from synlay/feature/dialyzer_tweaks

Export types auth/0 and priv_set/0 for a better analyzing of backend implementations