Implement this method to perform additional processing in the same transaction as the Durable State upsert or delete.

The process method is invoked for each DurableStateChange. Each time a new Connection is passed with a new open transaction. You can use createStatement, update and other methods provided by the R2dbcSession. The results of several statements can be combined with CompletionStage composition (e.g. thenCompose). The transaction will be automatically committed or rolled back when the returned CompletionStage is completed. Note that an exception here will abort the transaction and fail the upsert or delete.

The ChangeHandler should be implemented as a stateless function without mutable state because the same ChangeHandler instance may be invoked concurrently for different entities. For a specific entity (persistenceId) one change is processed at a time and this process method will not be invoked with the next change for that entity until after the returned Future is completed.