[TECH] default test run to exclude integration tests

[pilosus]

To do:

• separate unit tests from integration tests
• by default (lein test) run only unit tests to save time
• run full test suit including integration tests in docker with a dedicated selector (longer run for CI)

[pilosus]

Won't fix:

• too many integration tests we rely on
• namespaces with integration tests run fixtures that often don't work locally
• it's easier to run non-integration tests with clojure -X:dev:test :vars '[dienstplan.db-test/test-rota-update!]' locally