By default, the spotless Maven plugin binds its check goal to the verify
phase (late in the lifecycle, after integration tests). Because we
currently only run `mvn test` for CI, it doesn't proceed as far as
verify so missed formatting is not caught by CI.

This binds the check to an earlier phase, in between test-compile and
test, so that it will fail before `mvn test` but not disrupt your dev
workflow of compiling main and test sources as you work. This strikes a
good compromise on failing fast for code standards without being _too_
nagging.

For the complete lifecycle reference, see:
https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html