fix: header converter CloudEvents not supported

Author: teoincontatto

stackgres-k8s/src/stream/src/main/java/io/stackgres/stream/jobs/source/AbstractPostgresDebeziumEngineHandler.java

@@ -132,7 +132,7 @@ public <T> CompletableFuture<Void> streamChangeEvents(
     try {
       engine = DebeziumEngine
           .create(
-              KeyValueHeaderChangeEventFormat.of(format, format, format),
+              KeyValueHeaderChangeEventFormat.of(format, format, null),
               engineBuilderFactory)
           .using(props)
           .using(new ConnectorCallback() {