Secrets injection using sops-nix after the switch is done.

[niksingh710]

Mic92/sops-nix#728 (comment)

as this issue mentions the required case of injecting a value from sops-nix.
sops exposes a file path that contains tha key.
cat file/path reveals the secret.

rn it is possible to inject that value in a config file by using runCommand but that changes whole content of the file making other options related to that config useless.

my proposal is that home-manager option value can accept sops path.

nix.settings = {
    experimental-features = [ "nix-command" "flakes" ];
    show-trace = true;
    secret = home-manager.lib.fetchSecret config.sops.secret.path;
  };

if the secret path is valid then secret key is set in the final config, and if path is invalid then that entry is ignored. (this is done after the build is done and in repl secret should show a Secret type enum for secret)