Use clearer example data in unit tests

Right now we use "config" as a mode, which is kind of confusing. We should make it "debug" mode or something.

Also, maybe "version" would be a better example scope than "subject_id". I haven't super thought through it, but I think a "version" scope would be a good way to handle deploying major version updates to apps, and the awkward period of time when you need to support multiple versions with different config schemas running in various places.