code: public void addExtension(String name) throws Exception {
          // /extension=<name>/:add(module=<name>)
          final ModelNode request = createRequest(ADD, Address.root().add(EXTENSION, name));
          request.get(MODULE).set(name);
          final ModelNode response = execute(request);
          if (!isSuccess(response)) {
              throw new FailureException(response, "Failed to add new module extension [" + name + "]");
          }
          return;
      }
docs: Adds a new module extension to the core system.
  
  @param name the name of the new module extension
  @throws Exception any error