nwdiag: Allow line border for group

Hello PlantUML team,

Could you allow line border for group, on nwdiag?

This example seems to not works...:

<style>
group {
  LineThickness 5
  LineColor red
}
</style>

Here is a full example:

@startuml
<style>
group {
  BackGroundColor palegreen

  LineThickness 5
  LineColor red
}
</style>

nwdiag {
  network N {
      w1;
      w2;
  }

    group {
    description = "long group label";
    w1;
    w2;
  }
}
@enduml

Especially to flat theme as amiga or other.... :

Thanks for the enhancement, Regards,

plantuml / plantuml

nwdiag: Allow line border for group #1226