nixos/mjolnir: explicitly set --mjolnir-config

  # these config files will be merged one after the other to build the final config

  configFiles = [

    "${pkgs.mjolnir}/share/mjolnir/config/default.yaml"

    "${pkgs.mjolnir}/libexec/mjolnir/deps/mjolnir/config/default.yaml"

    moduleConfigFile

  ];

      wantedBy = [ "multi-user.target" ];

      serviceConfig = {

        ExecStart = ''${pkgs.mjolnir}/bin/mjolnir'';

        ExecStart = ''${pkgs.mjolnir}/bin/mjolnir --mjolnir-config ./config/default.yaml'';

        ExecStartPre = [ generateConfig ];

        WorkingDirectory = cfg.dataPath;

        StateDirectory = "mjolnir";