Seems right. My initial models were not complete, as I didn't have a features app. Now I think I accidentally added some of my WIP.

This matches our data model anyway: https://docs.google.com/drawings/d/1tWhxPzuBWYWlxoo4mueNnkUcSG3HrK6691bS6XbQ_xw/edit?pli=1 (it would be good to keep the diagrams up to date if we introduce changes, and maybe convert to a format we can put under version control?)