code: protected function enrichEventMetadata(Message $domainEvent, string $aggregateId): Message
      {
          $domainEvent = $domainEvent->withAddedMetadata('_aggregate_id', $aggregateId);
          $domainEvent = $domainEvent->withAddedMetadata('_aggregate_type', $this->aggregateType->toString());
  
          return $domainEvent;
      }
docs: Add aggregate_id and aggregate_type as metadata to $domainEvent
  Override this method in an extending repository to add more or different metadata.