The CustomerIdentifier parameter is scheduled for deprecation on March 31, 2026, per AWS API documentation. Instead, all logic should prefer the newer CustomerAWSAccountID.

Acceptance Criteria:

• Replace all usage of CustomerIdentifier with CustomerAWSAccountID in AwsBillableUsageAggregateConsumer.
  • https://github.com/RedHatInsights/rhsm-subscriptions/blob/c04aa20d3b7406c6045ec012672b7939f1788a3e/swatch-producer-aws/src/main/java/com/redhat/swatch/aws/service/AwsBillableUsageAggregateConsumer.java#L310

• Ensure resulting logic continues to function correctly with the updated field.