Compliance tests/documentation

Problem/Motivation

i

One of the tricky thngs about this module is compliance:
- understanding what the requirements are
- meeting them
- being sure that we have met them
- potentially proving that we meet them

I'm wondering how we can best document and test our complicance.

Proposed resolution

1. Commit the requirements quotations from 🌱 Product requirements Active as an hmrc_guidance.md
2. Create a compliance.md that goes through the guidance and gives notes on all the config and code features relevant to it
3. Create a Compliance folder of Kernel and Functional tests that explicitly test many compliance scenarios, and include references to the guidance points being tested.

Remaining tasks

Discuss.