Enable specifying a private gallery during update/installation of an offline installation layout (Response.json)

[lviolette]

Apologies if this is already possible. I've not been able to find directions on it.
We use an offline layout for engineers to update or install Visual Studio.
We specify some custom things in our response.json file. It would be great if we could specify our private gallery there too?
I already have an atom feed.xml that points to our custom gallery. So if I could have it configured when installing/updating that would be great!

I also added a feature request in Developer Community:
https://developercommunity.visualstudio.com/t/Add-ability-to-configure-an-offline-Visu/1703515?entry=myfeedback