[Bug]:ElasticsearchStore无法保存自定义数据payload

**Describe the bug**
在RAG中如果使用ElasticsearchStore，无法保存DocumentMetadata中的自定义数据payload
代码如下：

<img width="966" height="626" alt="Image" src="https://github.com/user-attachments/assets/0d9279d1-c072-4d3a-98a3-2f7e78daa4bc" />

**Environment (please complete the following information):**

- AgentScope-Java Version: 1.0.10
- Java Version: 17
- OS: windows
