https://github.com/serokell/serokell.nix/blob/master/modules/vault-secrets.nix
https://github.com/serokell/vault-secrets

https://github.com/balsoft/nixos-config/blob/master/modules/secrets-envsubst.nix

2020
https://www.reddit.com/r/NixOS/comments/k0utpw/our_new_nix_deployment_tool_deployrs/