Kafka (KRaft) Cluster Running on Systemd-Nspawn

Hey all! This is the first in a series of 'recipes' I am writing demonstrating how to use `systemd-nspawn`/`machinectl` to containerize services for either production or development.

I'm personally optimistic about Kafka'a new KRaft protocol and am excited to see it gain independence in the ecosystem, so I started here.

If anyone finds these interesting or helpful, I would be curious to hear what other `systemd-nspawn` style containerization examples people would like to see!