Kafka producer bootstep

Addresses #385 (closed).

This is a WIP. In particular, I'm not sure if the send() method should live inside the Producer, and what other arguments it should have.

The Kafka bootstrap configuration is also currently a placeholder.

To-dos:

• Add new packages as dependencies (currently suffering from the htcondor dependency issue on Macs)
• Choose between python-confluent-kafka, adc-streaming, and hop-client (or some combination) [updated Feb 7, 2022]
• Add correct host to configuration