Will document this in a separate PR. The broad strokes are this:
1. to load through an attribtue, `load(attribute: [:nested: :stuff])`
2. to load through a calculation, `load(calculation: {:%{...input}, nested: :stuff})`
3. union types support loading through them, and is done first by keying by the type name, i.e: `load(union: [type_name: [nested: :stuff])`.
4. union types support specifying a load statement for all types with `load(union: [*: [nested: :stuff]])`
