code: public RouteBuilder action(String action) {
          boolean hasActionSegment = false;
          for (Segment segment : segments) {
              hasActionSegment = segment.action;
          }
  
          if(action!= null && hasActionSegment){
              throw new IllegalArgumentException("Cannot combine {action} segment and .action(\"...\") method. Failed route: " + routeConfig);
          }
  
          this.actionName = action;
          return this;
      }
docs: Name of action to which a route is mapped.
  
  @param action name of action.
  @return instance of {@link RouteBuilder}.