DORA Scores: Deployment frequency score is based on number of deployments instead of deployment frequency

Summary

Looking at the code ee/app/services/dora/aggregate_metrics_service.rb deployment frequency score data comes directly from Analytics::DoraMetricsAggregator which does NOT return frequency, but returns number of deployments.

Suggestion

• Use Dora::AggregateMetricsService which also transforms deployment count data to frequency based on given period.
• Add integration test for DoraPerformanceScoreCalculator
• Schedule background migration to recalculate existing records to use proper deployment frequency data.