Move Nix binary cache to a non s3 domain name

[lf-]

Bug report

Having the binary cache directly on an s3 domain name is a significant risk for not being able to fix a situation of excessive s3 transfer cost or migrate to different hosting.

It should be moved behind a CNAME alias on a domain you control for now so it could e.g. have a CDN in front like cache.nixos.org or allow migration to different hosting without changing external clients.

[olirice]

thanks for opening, good point

As this is a prototype we may not rush to fix it until we decide to invest in the project for production, but I'll leave this open to keep track of the issue