FIX: Wizard could not send custom color schemes to the client correctly (PR #10484)

This was likely introduced with the refactor to make ColorSchemeColor a database object. Add a test so this doesn’t happen again.

Also test other basics of the WizardSerializer.

For some reason, the .as_json left Ruby objects in; I solved this with a round trip through JSON during the test.

GitHub

notify on submit: https://meta.discourse.org/t/a-secret-message/161336/

lint failiure is not mine