default SubflowState createSubflowState(final Flow flow, final String stateId, final String subflow) {
        return createSubflowState(flow, stateId, subflow, null);
    }
Create subflow state subflow state.

@param flow    the flow
@param stateId the state id
@param subflow the subflow
@return the subflow state
api/cas-server-core-api-webflow/src/main/java/org/apereo/cas/web/flow/CasWebflowConfigurer.java