Pkg Proxy Cache / Automatic Mirror of installed packages

We use Julia in a commercial context. The more productive things get, the more paranoid we are. Julia relies on the github repository of a dependency staying where it is. If it disappears, the package can not be installed. See here.
Up to now, I’ve only found projects that mirror all Julia packages which (see this thread.)

I’m looking for a “caching proxy” solution, i.e. Pkg.add looks in our registry for the version and package you want and if not there gets it from github, mirrors it into our registry and installs it on your machine.

For languages such as Java, Python, R or Javascript we can use something like Nexus.
Is there anything similar for Julia yet?

I think that JuliaTeam is probably going to be the answer here.