Timeframe for Metrics

Currently, the Metrics Controller in the Keptn Lifecycle Toolkit only allows querying a single value per metric. This project will enable users to define timeframes for metrics and get standardized aggregated results for the given timeframe. The addition of time frames for metrics would provide developers with a lot of flexibility when analyzing their application’s performance as they would be able to easily switch between different timeframes to get a better understanding of how their application is performing. This can be achieved by modifying the structure of the Metric CRD by adding certain fields and then modifying the APIs of our Metric providers to support these newly added fields. The metrics controller would be able to query metrics over a timeframe and then return raw values from the providers which can then be passed to the aggregation functions to calculate the desired aggregated value. These values would be updated in the Metric CRD.