Expose Kafka Producer and Consumer Configuration

[Steve Glover]

There are many configuration settings for Kafka Producers and Consumers (see https://kafka-python.readthedocs.io/en/master/apidoc/KafkaProducer.html). Currently, Ignition does not allow any of these to be configured on a per-deployment basis. Ignition should allow these to be set through its normal configuration mechanism, ideally as a set of properties in the configuration that can be used verbatim to configure the Producers and Consumers.

[Steve Glover]

Kafka Producer, Consumer and AdminClient configuration can now be configured as follows in the configuration file:

messaging:
    # Kafka connection url
    connection_address: foundation-kafka:9092
    config:
        # timeout waiting for initial version check on Kafka producer/consumer initialisation
        # 5000ms is usually sufficient, increase if problems with NoBrokersAvailable occur
        api_version_auto_timeout_ms: 5000

Any properties under messaging.config will be used to configure KafkaProducer, KafkaConsumer and KafkaAdminClient instances.