Ahh! Thanks a lot for clarifying. It is much clearer now! 
So, to achieve the same with messaging, we could use a simple process that publishes the Order domain events to a message broker like Kafka, in which case the events would be published to a topic called PaymentIntegration. Did I get this right?
Sorry for the beginner question: How would the mapping between domain events and integration events look like? How do they differ from each other? Currently, I am using the same events for both domain and integration events.