hei! we are testing the upsert-kafka connector in order to create temporary tables but we have one question. When defining the columns how can we map the column names to certain fields. We are reading from a kafka topic containing protobuf and we would like , for instance, a certain column named "userId" to be mapped with a value from the protobuf called "value.event.customer.userId" How can we do this mapping? We could not see any example of this. Thanks!