Use json encoders to handle IO

[tylerflex]

Right now we use the standard .json() method from pydantic and our own logic to do some encoding.

see #2099

It would be better in the long run to implement json encoders to do this more generally and have it integrated better with the json package.

Either through pydantic directly
https://docs.pydantic.dev/1.10/usage/exporting_models/#json_encoders

Or using the json package
https://docs.python.org/3/library/json.html