Replace Poison with Jason [WIP]

[richeterre]

Since Jason requires an explicit @derive where we specify which fields will be encoded, my initial idea was to whitelist the fields in one place (the ecto_encoders.ex file) instead of spread around schema files.

However, a much nicer solution would be to write a function that takes in a %Performance{} struct and recursively

• removes Ecto.Association.NotLoaded fields (or at least set them to nil)
• removes struct and meta fields
• removes "private" fields that aren't needed to populate the registration form

Unfortunately, I can't figure out how to write such a filter since Elixir structs don't implement the Enumerable protocol 😕

[richeterre]

Closing this as it's made obsolete by #26 🥳