Class-based GraphQL Schema Definition

[toastercup]

Please see: https://github.com/rmosolgo/graphql-ruby/blob/master/CHANGELOG.md#180-17-may-2018

This is what we've been holding our breath for, and will enable us to have flexible schema definitions. We'll be able to dynamically, at runtime, determine what fields/etc to expose based on the user's/tenant's ContentTypes and permissions. As it stands right now, we implement an unacceptable, hacky solution to get part of the way there.

We have an old user story for this from when v1.8 was in alpha: https://careerbuilder.atlassian.net/browse/CE-733