Python 3.11 is now required, old versions were causing unpredictability in tests. (Sanic does not yet
support 3.12)
Sanic has been upgraded to 23.6.0, which is the latest version that avoids this bug:
https://github.com/sanic-org/sanic/issues/2921
New strategy for multiprocessing is to create all multiprocessing tools in one process, then fork
to other processes. The previous strategy was to declare multiprocessing tools at the top of every
file, or wherever they were needed at import/creation. Now all multiprocessing tools are attached to the
app.shared_ctx. This means `api_app` is imported in many, many places.
This forced a change in how the DownloadManager works. Previously, it would continually run
download workers which would pull downloads from a multiprocessing.Queue. Now, a single worker checks
for new downloads and sends a Sanic signal.
Flags have been reworked to use the `api_app`. I removed the `which` flag functionality because the
`which` are called at import and needed their own multiprocessing.Event.
