By specifying `key`, we get a different lazy batch loader for each
repository, which means that accessing a lazy object from one repository
will only result in that repository's objects being fetched, not those
of other repositories, saving us some unnecessary Gitaly lookups.
This allows the user to get a single MR nested in a GraphQL project
query.
Since we need the full path and the iid anyway, this makes more sense
than having a root query that needs the full path as well.
- All definitions have been replaced by classes:
http://graphql-ruby.org/schema/class_based_api.html
- Authorization & Presentation have been refactored to work in the
class based system
- Loaders have been replaced by resolvers
- Times are now coersed as ISO 8601
