Merge der Upgrades für Confluent/Spring-Boot (Branch 'rest-producer')

diff --cc docker-compose.yml
Simple merge

diff --cc src/main/java/de/juplo/kafka/RestProducer.java
index ac9a541,7d9bf12..6e4236b
--- 1/src/main/java/de/juplo/kafka/RestProducer.java
--- 2/src/main/java/de/juplo/kafka/RestProducer.java
+++ b/src/main/java/de/juplo/kafka/RestProducer.java
@@@ -4,6 -4,8 +4,7 @@@ import lombok.extern.slf4j.Slf4j
  import org.apache.kafka.clients.producer.KafkaProducer;
  import org.apache.kafka.clients.producer.ProducerRecord;
  import org.apache.kafka.common.serialization.StringSerializer;
 -import org.springframework.http.MediaType;
+ import org.springframework.http.HttpStatus;
  import org.springframework.web.bind.annotation.*;
  import org.springframework.web.context.request.async.DeferredResult;