confluent and kafka version mismatch

[darin-reify]

as currently written there's an explicit mismatch between confluent and apache kafka versions:

• confluent is pinned to version 6.1.6 which only supports kafka 2.7.0
• kafka is pinned to version 2.8.0

this isn't showing up as an issue because of the way leiningen resolves dependency conflicts. however, it does show up when trying to use this library as a gitlib via tools.deps.

tools.deps uses the most recent version which causes problems starting up streams since they now rely on the org.apache.kafka.common.Uuid class which doesn't exist before 2.8.0 (since 6.1.1-css will be used as the "latest version" for streams).