apollo-portal/src/main/java/com/ctrip/framework/apollo/openapi/v1/controller/ItemController.java/ItemController/deleteItem
class ItemController:  @PreAuthorize(value = "@consumerPermissionValidator.hasModifyNamespacePermission(#request, #appId, #namespaceName, #env)")
  @DeleteMapping(value = "/apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName}/items/{key:.+}")
  public void deleteItem(@PathVariable String appId, @PathVariable String env,
                         @PathVariable String clusterName, @PathVariable String namespaceName,
                         @PathVariable String key, @RequestParam String operator,
                         HttpServletRequest request) {

    if (userService.findByUserId(operator) == null) {
      throw new BadRequestException("user(operator) not exists");
    }

    ItemDTO toDeleteItem = itemService.loadItem(Env.valueOf(env), appId, clusterName, namespaceName, key);
    if (toDeleteItem == null){
      throw new BadRequestException("item not exists");
    }

    this.itemOpenApiService.removeItem(appId, env, clusterName, namespaceName, key, operator);
  }