Add nats support

[nathanejohnson]

NATS is now supported by clickhouse, so I decided it would be a lot nicer to lab up nats for proof of concept work than a full kafka cluster. This doesn't support jetstream yet, since clickhouse doesn't support it yet, but that's why I haven't implemented any retry logic as that seems to be a feature they're working towards. I'm not sure if this is code you'd be interested in merging, but I thought I would throw it out there just in case you see value in it.