https://github.com/Mic92/sops-nix

2023
vimjoyer - NixOS Secrets Management | SOPS-NIX of 6:34
    https://www.youtube.com/watch?v=G5f6GC7SnhU
    https://github.com/vimjoyer/sops-nix-video
2022
https://bmcgee.ie/posts/2022/11/getting-nixos-to-keep-a-secret/

samples
https://github.com/krupkat/gcp-nixos/blob/main/howto.md