extra field require

**Is your feature request related to a problem? Please describe.**

in some case, I want to store some business key in one point data, as I know, no framework has implement include influxdb, openTSDB and so on, but I found [nightingale](https://github.com/didi/nightingale) support **extra** field in [this api](https://n9e.didiyun.com/docs/api/data/)

首先检查所请求的额外字段和链接的 Nightingale data API，然后检查 repository 中与数据摄取和点表示相关的部分。明确 business key 应如何表示、接受、存储和返回，并在实现之前定义能够展示预期行为的测试。

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