If you have Docker installed, run docker-compose -p ascii-rect up -d to start the services.
Then, to setup the Phoenix server: mix deps.get && mix ecto.reset should get your database seeded and ready to go.
And to start the server: iex -S mix phx.server.
With the database seeded, you can select a canvas.external_uuid and CURL it:
curl http://localhost:4000/api/canvases/<external_uuid>// TODO
// To create a canvas, you'll POST to
curl -X POST http://localhost:4000/api/canvases