code layout for all attestation / token negotiation stuff

Per yesterday's meeting, the layout is in the following diagram. Note you can always find it as part of README of the attestation repo.

code-layout

This looks much clearer than the sketch in the meeting. I always find it hard to read the sketch, perhaps because I am not used to the font :upside_down_face:

That was my hand writing so I can't change font at all, sorry!