Re-structure internals

Some of the internals to this library are a bit strange and confusing:

- Acknowledgement Handlers, do the actual reading of data from the queue.
- The client implements all the interfaces, and the adapter implements all the methods, but might only implement some of the functionality.

Start by mapping the responsibilities described for the Acknowledgement Handlers, client, and adapter. Clarify which component should read queue data, expose interfaces, and provide functionality before proposing a restructuring. The issue does not name files, tests, or a defined completion condition.

Scritto dal modello di indicizzazione a partire dal testo della issue.