feat: Add Booklooker client configuration and exception handling

- Introduced BooklookerConfig class for runtime configuration management.
- Created custom exceptions for API errors, including authentication and validation errors.
- Generated API contracts from OpenAPI specification, including endpoints and security schemes.
- Implemented models for articles, orders, and webhooks to facilitate data handling.
- Developed a webhook helper for processing and enriching webhook events.
- Added tests for configuration defaults, token expiration, and webhook enrichment.

README.md

@@ -0,0 +1,36 @@
+# booklooker-client
+
+A Python client for the Booklooker REST API designed for middleware and connector-hub scenarios.
+
+## Highlights
+
+- Generated API contract derived from [openapi.yaml](openapi.yaml)
+- Sync and async client entrypoints
+- Pydantic models for normalized responses
+- Token auto-refresh handling
+- Webhook helper toolbox for Push-API style events
+- FastAPI example receiver and enrichment workflow
+
+## Installation
+
+```bash
+pip install -e .[dev,webhooks]
+```
+
+## Quick start
+
+```python
+from booklooker_client import BooklookerConfig, SyncBooklookerClient
+
+config = BooklookerConfig(api_key="YOUR_API_KEY")
+client = SyncBooklookerClient(config)
+
+token = client.authenticate()
+articles = client.get_article_list()
+print(token.token)
+print(articles.items)
+```
+
+## Notes
+
+Booklooker wraps nearly all responses into a generic envelope with `status` and `returnValue`. This package normalizes those responses into typed Pydantic models so downstream middleware can work with stable structures.