Split up the Github workflow. Instead of one workflow with two jobs, one
to build the Docker image and one to test it, split it into two separate
workflows, one to build and one to test. This way if the Docker build
fails it doesn't try to run the tests, and if the tests fail it only
marks the test workflow as failed, not the entire workflow.
This is especially so the workflows page doesn't show everything as
failing just because the tests failed.
https://github.com/danbooru/danbooru/actions
39fa2fe02d