ProduceToTopic does not allow to add custom headers to messages

[nikitasharma1108]

ProduceToTopic.py line 118
for k, v in producer_callable():
producer.produce(
self.topic, key=k, value=v, on_delivery=self.delivery_callback
)

does not pass headers, so unable to send custom headers with messages

[dylanbstorey]

we accept pull requests.

[nikitasharma1108]

I have sent a Pull request