nwdiag: allow nested groups

[dgutson]

I know this may depart from the original nwdiag specification, but it would be useful to nest groups (at least 1 level).

@startuml
nwdiag {
  group singleNode {
      group system1 {
         container11;
         container12;
      }

      group system2 {
         container21;
         container22;
      }
    }

    network N {
         container11;
         container12;
         container21;
         container22;
    }
}

[dgutson]

This would neatly align with the C4 model.

[The-Lum]

Hi all,

That is currently not available, see: https://github.com/plantuml/plantuml/blob/a171a90403783312c2e49d1b7506fd3a8fc2aaf4/src/net/sourceforge/plantuml/nwdiag/NwDiagram.java#L131-L133

💡 That is now a wanted feature.

Regards.

[jasonculligan]

+1 - need this to show sub trust boundaries