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

Start by locating the existing API routes for analytics and deployment history, then trace how deployments are represented within the requested timeframe. Define how repeated successful versions identify rollback events and how their start, stop, duration, and percentage rate should be represented in the response. Done means the route returns those fields for the specified timeframe and has coverage for the calculation.

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