apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/AppController.java/AppController/create
class AppController:  @PostMapping("/apps")
  public AppDTO create(@Valid @RequestBody AppDTO dto) {
    App entity = BeanUtils.transform(App.class, dto);
    App managedEntity = appService.findOne(entity.getAppId());
    if (managedEntity != null) {
      throw new BadRequestException("app already exist.");
    }

    entity = adminService.createNewApp(entity);

    return BeanUtils.transform(AppDTO.class, entity);
  }