Add Async support with AsyncClient and AsyncOauthClient #5

[Deadpool2000]

This PR addresses the issue where the SDK was blocking the event loop in async frameworks like aiohttp or FastAPI. I've added full asynchronous support and improved resource management across the board.

What's new?

• Async Clients: Introduced

1. AsyncClient
2. AsyncOauthClient . These use httpx.AsyncClient under the hood to handle non-blocking I/O.

• Context Manager Support: All clients (both sync and async) now support context managers (with and async with). This ensures that the underlying connection pool is properly closed after use, preventing resource leaks.

• Simplified Imports: You can now import clients directly from the package root: from openapi_python_sdk import Client, AsyncClient

• Better Tests: Added a new test suite for the async implementation using IsolatedAsyncioTestCase (standard in Python 3.10+).

Quick Usage Example

from openapi_python_sdk import AsyncClient
async with AsyncClient(token="YOUR_TOKEN") as client:
    data = await client.request(
        method="GET",
        url="https://api.example.com/endpoint"
    )

Verification

• Ran existing 10 sync tests (all passing).
• Added 4 new async tests covering authentication and generic requests (all passing).
• Total coverage: 14/14 tests passing.

Updated the README.md with these usage examples to help users get started.

Let me know if you have any feedback!