public KafkaSourceBuilder<OUT> setRackIdSupplier(SerializableSupplier<String> rackIdCallback) {
        this.rackIdSupplier = rackIdCallback;
        return this;
    }
Set the clientRackId supplier to be passed down to the KafkaPartitionSplitReader.

@param rackIdCallback callback to provide Kafka consumer client.rack
@return this KafkaSourceBuilder
inlong-sort/sort-flink/sort-flink-v1.18/sort-connectors/kafka/src/main/java/org/apache/inlong/sort/kafka/source/KafkaSourceBuilder.java