kafkaTemplate in KafkaItemWriter should be protected

[fmbenhassine]

As of v4.3.0, the kafkaTemplate field in KafkaItemWriter is private. This makes it impossible to use the template in overridden methods like writeKeyValue or write:

KafkaItemWriter<String, String> myCustomKafkaItemWriter = new KafkaItemWriter<String, String>() {
	@Override
	public void write(List<? extends String> items) throws Exception {
		// unable to use super.kafkaTemplate here
	}
};

The visibility of the field kafkaTemplate in KafkaItemWriter should be changed from private to protected.

[adityausathe]

I have opened PR #3807 to address this. @benas please review.

[fmbenhassine]

Resolved with #3807 .