audit Domain Metrics should be rolling and calculated per AuditEvent insertion

[amydevs]

Specification

As metrics are implemented on a case by case basis for each metric, this may not apply to all metrics.

However, for:

• averages
• max
• min
• totals

Metrics should be stored in the database and updated per insertion of a related AuditEvent

Additional context

• Setup audit domain for tracking user/action events and metrics #628

Tasks

1. Implement rolling average/total for connection audit metrics.