Add the reload option to the server

[jdavid]

Useful in development, with this option changes to the code are detected and the server is automatically restarted.
But this is not easy to do right now (I've tried). It will be easier once Kludex/uvicorn#2445 is merged.

We would need to change:

# Now
uvicorn.run(app, ...)

# After
uvicorn.run("caterva2.services.sub:app", ..., reload=True)

The problem then is passing the configuration to the app. The PR above should make it easy.