v2.1.0: Add support for OIDC/OAUTHBEARER Authentication

This release includes #53 by @lpsinger which enables the new(ly enhanced) OIDC authentication mechanism supported by the latest (version 3.1.0) Apache Kafka release. When not using this new feature this release remains compatible with older Kafka versions.

Also included is a bug-fix to avoid crashing when attempting to read a topic with multiple partitions 'to its end' while new messages are being actively published.