Actually, now that I think of it – the other migration sets it using the generic `stream_base` config property from Matterhorn, while this one uses the `stream_base` from the specific MasterFile workflow if it's available. They won't clobber each other. That one sets a default, and this one sets it based on the configuration at the time of transcoding if it can. We could leave them alone, or combine them here such that `stream_base` is ||='ed.