ProGet is a package, artifact, and Docker repository that can host private packages as well as proxy public repositories like NuGet.org, Npmjs.org, PyPi.org, etc.
It's already available as a Docker image:
https://docs.inedo.com/docs/installation-linux-docker-guide
Based on the tutorial, it seems like it wouldn't be too difficult to make into an app. However, ProGet depends on SQL Server, which doesn't seem to be supported as an Add-on just yet 
So perhaps I should edit this post to say, "SQL Server" first? 