WIP: Set up workflow for UML diagrams
Context
We're planning to use UML to model parts of the existing system, design the new architecture, and document the new system. PlantUML is a tool that lets us store these diagrams as declarative code and export them in whatever image or document format we need.
Overview
In this merge request, I've set up a simple workflow that we can use for now: write your PlantUML diagrams locally, run the make job to generate PNGs, and commit everything to this directory (see included README for details). There are ways we can automate this that I'm still evaluating, but this should be enough for our purposes right now.
I also started working on a UML diagram of the existing architecture (mostly going over the one @giac91 provided and making sure it's up to date), but @jroiseaux or I will add that in another MR coming soon and replace the test files I have here.
How was this tested?
Tested the diagram generation on Linux with plantuml installed through the package manager -- this should behave the same on Mac if PUML is installed via Homebrew or on other Linux distros. Not sure about Windows, if we have interested people on Windows workstations I'll need their help testing PlantUML there since I don't have one handy.