code: public void createStateDefaultTransition(final TransitionableState state, final String targetState) {
          if (state == null) {
              LOGGER.trace("Cannot add default transition of [{}] to the given state is null and cannot be found in the flow.", targetState);
              return;
          }
          val transition = createTransition(targetState);
          state.getTransitionSet().add(transition);
      }
docs: Add a default transition to a given state.
  
  @param state       the state to include the default transition
  @param targetState the id of the destination state to which the flow should transfer