Added a consumer, that received messages of multiple types

[demos/kafka/kafkahandler] / src / main / resources / application.yml

spring:
  kafka:
    bootstrap-servers: :9092
    consumer:
      group-id: multi
      auto-offset-reset: earliest
      value-deserializer: org.springframework.kafka.support.serializer.JsonDeserializer
      properties:
        spring.json.type.mapping: "foo:de.juplo.kafka.Foo,bar:de.juplo.kafka.Bar"
        spring.json.trusted.packages: "de.juplo.kafka"
logging:
  level:
    root: INFO