Testing the ideal flow for QubesOS and Guix foreign

From my last thoughts about which flow use, I'm trying now to setup the whole user preferences inside the TemplateVM, making it generic enough to meet the main daily needs.

Planned steps:

1. Configure TemplateVM proxy to prevent completely connecting it to the internet.
2. Configure and first tests.
3. Reduce the persistence by customizing a smaller scope for bind-dirs.
4. Migrate from the manual guix install flow to a real Guix manifest.
   • I really want this layer, so I can use the same configurations outside the QubesOS.
5. Apply via SaltStack.