Reusable ExUnit conformance case for Gitility.RefDB.Backend modules.
The using module supplies backend_refs/0, returning at least two
Gitility.Ref values in strict byte order. The generated suite checks the
miss/error distinction, concurrent resolution, optional listing, provider
protocol validation, and end-to-end DTO conversion.
use Gitility.RefDB.Backend.Conformance,
backend: MyApp.Refs,
init_arg: :test_repository,
concurrency: 4