docs: @RequirePOST
      public HttpResponse doDiscard(StaplerRequest req, StaplerResponse rsp) {
          saveAndRemoveEntries( new Predicate<Map.Entry<SaveableReference,VersionRange>>() {
              @Override
              public boolean apply(Map.Entry<SaveableReference, VersionRange> entry) {
                  return entry.getValue().max == null;
              }
          });
  
          return HttpResponses.forwardToPreviousPage();
      }