I have some Django middleware code that connects to a database. I want to turn the middleware into a reusable application ("app") so I can package it for distribution into many other projects, without needing to copy-and-paste.

I don't understand where a reusable application is supposed to configure itself. Since it's intended for redistribution I don't have the ability to write the central settings.py myself. Looking at the Django documentation I see there's settings.configure but it appears to replace the entire configuration, instead of letting me "splice" a new database into DATABASES.

What's the right way to give my reusable middleware app the ability to configure its own database connection? I don't want it to interfere with the databases of applications where I'll be installing it. Thanks.

You could follow the approach of Django debug toolbar. It includes an app config class, and overrides the settings in the ready method.

You can see the code here.