Use dataclasses instead of tuples/dicts for passing data around

[snazzyfox]

We should formalize our data interface by using dataclasses instead of tuples and dictionaries when returning data. This can help in many ways

• eliminate the possibility of missing a key, mixing different casing, or making a typo by making these structure lintable
• much easier to document the meaning and data types of fields
• allows us to create computed properties that are only computed on demand instead of always generated with the model even if not always needed