handle assets and requests_pathname_prefix

So I currently have an API Gateway serving my Dash app under the /dev/ base path.
I have specified my Dash.dash app with

app.config.update({
    # as the proxy server will remove the prefix
    "routes_pathname_prefix": "/", 
    # the front-end will prefix this string to the requests
    # that are made to the proxy server
    'requests_pathname_prefix': '/dev/'
})

and most the app renders fine however, I noticed that the files in my assets directory are not being found since when the app loads, its looking in /assets/ instead of /dev/assets.

This seems like a quick fix on my part, but I'm not sure where to start since this library is so new to me.

Start by reproducing the Dash app behind an API Gateway at the /dev/ base path using the shown routes_pathname_prefix and requests_pathname_prefix settings. Trace how the assets directory URLs are generated and verify that asset requests use /dev/assets while the existing root-path behavior remains correct.