Integration tests without PostgreSQL

Parent: [EPIC] AURA Docker Compose Integration Test Suite (aura-tests#5 - closed)

Our GitLab integration test setup is quite complex, because tank still needs PostgreSQL for storing records. This may no longer be the case and might open up the possibility to reduce complexity of the test setup, allowing us to use the gitlab integration tests for local execution with tools like gitlab-ci-local and get rid of the duplicate test configuration with docker compose in tests/docker-compose.yml.