We need to:

1. Notice the broker has added a new partition (through consumer group rebalance notifications or otherwise)
2. Assign and start consuming that partition
3. Include that partition information in checkpoints henceforth

Also, we should refactor all the connection and partition management logic into Connector class (perhaps renaming it), see this discussion: https://github.com/10gen/mongo-enterprise-modules/pull/1976#discussion_r1509523144