Add a safir.events subpackage to Safir that will provide many common patterns needed by Roundtable apps that integrate with SQuaRE Events (Kafka):

• Set up SSL context for the Strimzi certificates
• Set up a Producer
• (maybe) add helpers for managing schemas from the app's local storage? I'm not sure we know the best pattern for this yet; or if it better belongs in Kafkit.

This will be developed alongside the LTD Events service (DM-23731)