nixos/modules/system/envfs.nix

inputs:
{
  options.nixos.system.envfs = let inherit (inputs.lib) mkOption types; in mkOption
    { type = types.nullOr (types.submodule {}); default = {}; };
  config = let inherit (inputs.config.nixos.system) envfs; in inputs.lib.mkIf (envfs != null)
  {
    services.envfs.enable = true;
    environment.variables.ENVFS_RESOLVE_ALWAYS = "1";
  };
}