apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/ItemSetController.java/ItemSetController/create
class ItemSetController:  @PreAcquireNamespaceLock
  @PostMapping("/apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName}/itemset")
  public ResponseEntity<Void> create(@PathVariable String appId, @PathVariable String clusterName,
                                     @PathVariable String namespaceName, @RequestBody ItemChangeSets changeSet) {

    itemSetService.updateSet(appId, clusterName, namespaceName, changeSet);

    return ResponseEntity.status(HttpStatus.OK).build();
  }