Review Error handling

[LCrossman]

Description

Error handling needs to be clear and more systematic. Errors particularly need to be clear for non-Rust folks.

Change Type:

• Refactoring

Current Structure:
Error handling is not systematic

Proposed Changes:
Decide best error handling e.g. custom type or anyhow error and implement consistently

Motivation

Error handling is not consistent and may be important for understanding

Potential Impact

Some changes may be necessary to improve consistency

[em-baggie]

Happy to pick this up and look at implementing consistent custom errors across the repo, feel free to assign to me if you're happy.