apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/controller/NamespaceBranchController.java/NamespaceBranchController/createBranch
class NamespaceBranchController:  @PreAuthorize(value = "@permissionValidator.hasModifyNamespacePermission(#appId, #namespaceName, #env)")
  @PostMapping(value = "/apps/{appId}/envs/{env}/clusters/{clusterName}/namespaces/{namespaceName}/branches")
  public NamespaceDTO createBranch(@PathVariable String appId,
                                   @PathVariable String env,
                                   @PathVariable String clusterName,
                                   @PathVariable String namespaceName) {

    return namespaceBranchService.createBranch(appId, Env.valueOf(env), clusterName, namespaceName);
  }