Analytics - Rollback Rate

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

A metric we would like to provide and graph on the analytics page is Rollback Rate. We can determine the rollback rate in a crude way by looking to see if a specific version was deployed successfully to the same environment twice. It would also be nice to provide the time difference between those events and we can possibly determine mean time to recovery (MTTR).

**Describe the solution you'd like**

Create an analytics route on the api that returns rollback events in the specified timeframe. These events should also include the start/stop time and duration. We should also provide a computed rollback rate as a percentage in the response.

**Describe alternatives you've considered**

None

**Additional context**

None

先找出現有的 analytics 和部署歷史 API 路由，接著追蹤部署在要求的時間範圍內如何表示。定義如何透過重複成功的版本識別 rollback 事件，以及如何在回應中表示其開始、停止、持續時間和百分比率。完成的條件是該路由針對指定的時間範圍回傳這些欄位，且計算具備涵蓋範圍。

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