@Override
    public PageService<NamespacePluginQueryCondition, NamespacePluginVO> pageService() {
        return namespacePluginService;
    }
query plugins by namespace.

@param namespace namespace.
@return {@linkplain ShenyuAdminResult}
shenyu-admin/src/main/java/org/apache/shenyu/admin/controller/NamespacePluginController.java