Use scalafix to fix up the generated APIs

[DavidGregory084]

The APIs that are generated are a huge improvement for the most part in that they replace callbacks with Task.

However, I think we can do better, especially if we can use scalafix (in conjunction with refined?) to rewrite them in repeatable way.

Ideas include:

• Banishing the many Strings and Ints in favour of more precise types like String Refined Url and Int Refined Positive
• Wrapping side-effecty things in Task.eval