diachron uses `Call` and `Result` for its own types that wrap `Request` and
`Response`.

This hopefully will make things less confusing and avoid problems with shadowing.

## meta

- We use _algorithmic complexity_ for performance discussions, when
  things like Big-O come up, etc

- We use _conceptual complexity_ for design and architecture

- We use _cognitive load_ when talking about developer experience

- We use _operational burden_ when talking about production reality