Add tests workflow

[SHAcollision]

This PR adds automated integration testing for Nexus on Github.

Should block merges when tests are failing.

Pre-submission Checklist

For tests to work you need a working neo4j instance with the example dataset in docker/db-migration

• Code Quality: Clippy has been run with no warnings, cargo clippy
• Testing: Implement and pass new tests for all new code, while maintaining existing test suite, cargo test.
• Performance: Ensure new code has relevant performance benchmarks, cargo bench