Flexible Kafka Producer Node

This release contains a breaking change to the kafkaproducer node type. Formerly, kafkaproducer accepted events with a []byte payload.

For improved flexibility where the destination is not always a single hard-configured topic, the kafkaproducer now accepts a struct that implements the firebolt.ProduceRequest interface. This interface includes Message() which should return the same byte array payload as you previously used, and a new Topic() which if it returns a nonzero value will override the node's configured topic destination.

There is a trivial implementation firebolt.SimpleProduceRequest provided for use in basic cases.

This release also upgrades librdkafka to v1.3.0.

Correct Public Package Paths

Initial release module incorrectly retained our internal pathnames, fixed here.

Initial Open Release

This is the initial public release of firebolt; it's the exact same code that we use internally to power some of our observability pipelines.