docs: protected void registerMultifactorFlowDefinitionIntoLoginFlowRegistry(final FlowDefinitionRegistry sourceRegistry) {
          val flowIds = sourceRegistry.getFlowDefinitionIds();
          for (val flowId : flowIds) {
              val definition = sourceRegistry.getFlowDefinition(flowId);
              if (definition != null) {
                  LOGGER.trace("Registering flow definition [{}]", flowId);
                  this.loginFlowDefinitionRegistry.registerFlowDefinition(definition);
              }
          }
      }