When upserting a system during payg tally, look for possible duplicates via each identifier:
MetricUsageCollector.collectHour needs to check for instances matching any of the keys, regardless of INSTANCE_TYPE. NOTE this makes INSTANCE_TYPE mostly irrelevant, though it optimizes performance of long-lived SaaS.
keys:

• inventory_id
• insights_id
• subscription_manager_id
• instance_id

Testing

• Starting with a system record having one of the keys above, when a payg event has one matching identifier it should be treated as a matching system (a duplicate should not be made during payg tally, instead the existing record should be updated).