Allow users to use private repositories as a dotfiles repository

[gtsiolis]

Problem to solve

Dotfiles support was added back in #5198 and #7337, following the relevant RFC.

However, private repositories are not supported as described[1] in the RFC or something is not set properly. Cc @csweichel

This repo must either be public, or can be pulled using one of the authentication providers the user has signed in with.

See also relevant discussion from discord.

Proposal

While the next large step towards improving this feature is described in #7385, we could break things to even smaller pieces and work on an MVC (minimum viable change) to just allow users to use private repositories as a dotfiles repository. ➿

[gtsiolis]

@jldec could you 🅰️ verify if this is an issue and 🅱️ whether it's worth scheduling instead of waiting for #7385? Feel free to close if needed.

[iQQBot]

/assign