beam-sdks-java-io-kafka error with kafka brokers < 0.11

In beam 2.9.0, KafkaRecordCoder was used for both producer/consumer records in KafkaIO, in version 2.10.0, ProducerRecordCoder was introduced but it appears that in the following code checks are not made to ensure kafka client compatibility:

https://github.com/apache/beam/blob/master/sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/ProducerRecordCoder.java#L137

Specifically the method call to `headers` will fail for kafka clients < 0.11. Elsewhere in this class there are checks on ConsumerSpEL and it is proposed that they should be reused in the line referenced.