Make the SDK Async-friendly

If folk want to use this SDK in an async/non-blocking environment like [FastAPI](https://fastapi.tiangolo.com/) they will not have a good time. We should move to using async-friendly libraries.

Start by reviewing the SDK's current synchronous dependencies and public API, then compare them with the requirements of a non-blocking FastAPI application. Identify the libraries and interfaces that would need to change, and confirm the expected async usage before implementation. Done means the SDK can be used without blocking an async application.

Written by the indexing model from the issue text.