@GetMapping("/queryRootTag")
    public ShenyuAdminResult queryRootTag() {
        return ShenyuAdminResult.success(ShenyuResultMessage.QUERY_SUCCESS, tagService.findByParentTagId("0"));
    }
query root tag.
@return {@linkplain ShenyuAdminResult}
shenyu-admin/src/main/java/org/apache/shenyu/admin/controller/TagController.java