Created by: tsenart
This commit introduces an initial GraphQL schema for the a8n product.
To help reviewing, it makes the necessary changes to allow us to use GraphQL schema extension, rather than bundling everything in a single file.
Once we discuss, iterate and agree on this schema, we'll merge it and proceed to implement it, using both prototype code and new code as appropriate.
Push commits to the source branch or add previously merged commits to review them.
