Rails - Single Table Inheritance

https://medium.com/@dcordz/single-table-inheritance-using-rails-5-02-6738bdd5101a

https://huzefabiyawarwala.medium.com/single-table-inheritance-in-rails-fc28a56a3f9

https://stackoverflow.com/questions/555668/single-table-inheritance-and-where-to-use-it-in-rails

https://old.alexreisner.com/code/single-table-inheritance-in-rails - very good overview of which options, we'll typically have, when faced with a design problem