anchor.diff:              read shell
               read createHome
               read password
  +            read isSystemUser
   
               if ! curEnt=$(getent passwd "$name"); then
  -                useradd --system \
  +                useradd ''${isSystemUser:+--system} \
                       --comment "$description" \
                       ''${uid:+--uid $uid} \
                       --gid "$group" \
  
positive.code:           }
          ];
  
        addAttrs =
          { name
          , description
  
negative.code:         , createHome ? false
          , useDefaultShell ? false
          , password ? null
          , isSystemUser ? true
          }:
          { inherit name description uid group extraGroups home shell createHome password isSystemUser; };
  
      in map addAttrs (defaultUsers ++ config.users.extraUsers);
  
  