Easier private sources

Discussed in https://github.com/microsoft/winget-cli/discussions/2168

^{Originally posted by aqua-nerd May 19, 2022}
Thought I would have a play with winget this week thinking maybe its come of age. Thought by now private sources would be an easy thing to do. It seems pretty convoluted to get a private source going since its basically just somewhere to host manifest files it should be able to work with any basic web server. I don't see the point in having to spin things up in Azure like Cosmos DB and other things I know nothing about just to host a few packages. Some of us are still on-prem shops and like most other Microsoft projects your leaving these shops behind! Then you have this guy trying to shill his winget.pro service all over the place, its super frustrating. Please make a reference winget rest source that we can run on-prem.

Ok rant over, I'm off to deploy a few packages via GPO like its 2008!

Start with discussion 2168 and inspect the repository's existing REST source implementation and deployment assumptions. Define done as a reference implementation that can host private package manifests on a basic web server or on-premises without the Azure services mentioned in the issue; no file or test is named, so the scope needs maintainer confirmation.