Add an additional field to the data in the knowledge base to store custom attributes of the data.

**例行检查**

[//]: # '方框内填 x 表示打钩'

- [x] 我已确认目前没有类似 features
- [x] 我已确认我已升级到最新版本
- [x] 我已完整查看过项目 README，已确定现有版本无法满足需求
- [x] 我理解并愿意跟进此 features，协助测试和提供反馈
- [x] 我理解并认可上述内容，并理解项目维护者精力有限，**不遵循规则的 features 可能会被无视或直接关闭**

**功能描述**
We need a field to filter out the knowledge in the knowledge base. It is best to have the corresponding API to operate.
**应用场景**
If my knowledge is timely, I need to limit some knowledge from being searched or delete it.
**相关示例**