Filing this ticket as a precursor to SERVER-65789 to begin work on an architecture guide for queryStats. As the project has proceeded the code has been changing rapidly, and it would be great to document or outline the current state of the world as we onboard more people on to the project. The exact requirements for this draft are unclear, but could include
1. Outline of the current state of the system
2. Summary of work done for M0/M1 (and any other completed milestones when this is picked up)

3. Code organization summary (Note the linked ticket – we may want to do some organization as part of this work)

4. Onboarding guide for this sub-system.