Merge branch 'pt-src-id' into 'main'

System source returns parent rupture set id

Closes #229

See merge request !394

src/main/java/gov/usgs/earthquake/nshmp/model/SystemRuptureSet.java

@@ -343,7 +343,7 @@ public class SystemRuptureSet extends AbstractRuptureSet<SystemRuptureSet.System
 
     @Override
     public int id() {
-      return index;
+      return SystemRuptureSet.this.id();
     }
 
     @Override