manual-website/module.nix

{ lib, pkgs, config, ... }:
with lib;
let
  cfg = config.services.ese-manual;
in
{
  options.services.ese-manual = {
    enable = mkEnableOption "ese-manual";
    hostName = mkOption {
      type = types.nullOr types.str;
      default = null;
      example = "manual.example.com";
      description = ''
        The hostname the application should be served on.
        If it is `null`, nginx will not be automatically configured.
      '';
    };

  };

  config = lib.mkIf cfg.enable {
    services.nginx = lib.mkIf (cfg.hostName != null) {
      enable = true;
      virtualHosts.${cfg.hostName} = {
        root = pkgs.ese-manual;
      };
    };
  };
}