title: How to set custom Partitioner for kafka in Flink 1.14.3?
body: <pre><code>    val mySink = KafkaSink.builder()
    .setBootstrapServers(bootstrapserver)
    .setKafkaProducerConfig(myproperties)
    .setDeliverGuarantee(DeliveryGuarantee.AT_LEAST_ONCE)
        .setRecordSerializer(
          new mycustomSerializer(mytopic,
                  schemaregistryurl)
  
        ).build()
  
  class mycustomSerializer(topic: String, schemaRegistryUrl: String) extends 
  KafkaRecordSerializationSchema[MyRecord]
  </code></pre>
  <p>Although the above code is working fine but i am unable to set the custom partitioner in above code</p>
  <p>I have gone through the documentation if we make mycustomSerializer using KafkaRecorderSerializationSchema.builder()
  then we can set easily but how to do that in above code ?</p>