What I have come to always do is just use ecto (if you’re not using it for DB you don’t need to bring in the postgres adapter) and just structure interaction points as casting schemas. This gives you a central place for documenting the types, constraints and form, allows you to use the validations in ecto (or write your own) in a pipeline fashion, allows you to define additional types to express fine-grained values automatically on cast, serialisation when going out back to whatever, and to then “type” your functions to only accept casted values (ecto types) to work with - plus provides a very easy way to have fine grained error messages if needed.
It’s a bit more boilerplaty but I’ve found the end result to be way better than anything else I’ve seen (in and outside elixir) without much additional work. I even cast login params now, because why not.
