[WH] Deduplicate configuration

[timmc-edx]

The producer and consumer code in event-bus-kafka both currently load the same config settings and create a schema registry client in the same way. These should be deduplicated into a config.py or something.

[timmc-edx]

I was playing around with some code for this: main...common-config Whoever picks this up, feel free to use that code or not. (The attrs thing might be overkill. Might just want a dict with string keys or whatever.)

[robrap]

Implementation PR: #20