consumer_with_config

This library only exposes the `PartitionConsumer` which is actually marked as depreciated in Rust version and `consumer_with_config` is suggested. Also it is very confusing on how this consumer consumes messages on restart does it start from first message how do i do manual offset commit strategy ?

Start with the exposed PartitionConsumer API and compare it with the Rust consumer_with_config API. Trace how consumer restart position and manual offset commits are represented, then define done as exposing the suggested configuration path and documenting the restart and commit behavior.

Written by the indexing model from the issue text.