Binary Cache Support

[SomeoneWeird]

This adds support for configuring Nix Binary Caches.

During setup, we'll allow users to opt-out (as most people will probably want?) of using the Foundation binary cache (https://nix.dogecoin.org) so that they don't have to compile pups such as Dogecoin Core, which typically take 20m+ on normal hardware.

This doesn't mean that the end users have to trust published binaries though, as Nix still does its fully deterministic verification of the built binaries to ensure nothing has changed.

[blendtwenty]

This adds support for - configuring - Nix Binary Caches.

On the point of 'configuring', at this stage is it just opting in/out of FDN binary cache or could users set their own desired desired cache?

[SomeoneWeird]

This adds support for - configuring - Nix Binary Caches.

On the point of 'configuring', at this stage is it just opting in/out of FDN binary cache or could users set their own desired desired cache?

Right now the former, but we'll add UI eventually for managing other caches, as other pup authors may want to provide their own alongside pups they publish.