v2.1.0-snapshot

Implement graph query in API v2 (#1009)

* feature (api-v2): Refactor v1 graph query code for v2.

* test (api-v2): Refactor v1 graph tests for v2.

* feature (api-v2): Represent graph query results as normal JSON-LD graphs (ongoing).

* test (api-v2): Add graph query e2e tests.

- Add configurable limits to graph queries.
- Make results deterministic for tests.

* docs (api-v2): Document graph route.

- Clean up code a bit.

* style (api-v2): Clean up code a bit more.