Add unit tests for authentication and webhook parsing

- Implement tests for basic and bearer authentication headers in `test_auth.py`.
- Create tests for the `EasybillWebhookParser` in `test_webhooks.py`, covering JSON and form-encoded payloads, as well as a generic parse and acknowledgement method.

generated/async/docs/WebHook.md

@@ -0,0 +1,36 @@
+# WebHook
+
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**content_type** | **str** |  | 
+**description** | **str** |  | 
+**events** | **List[str]** |  | 
+**id** | **int** |  | [optional] [readonly] 
+**is_active** | **bool** |  | [optional] [default to False]
+**last_response** | [**WebHookLastResponse**](WebHookLastResponse.md) |  | [optional] 
+**secret** | **str** |  | 
+**url** | **str** |  | 
+
+## Example
+
+```python
+from easybill_generated_async.models.web_hook import WebHook
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of WebHook from a JSON string
+web_hook_instance = WebHook.from_json(json)
+# print the JSON string representation of the object
+print(WebHook.to_json())
+
+# convert the object into a dict
+web_hook_dict = web_hook_instance.to_dict()
+# create an instance of WebHook from a dict
+web_hook_from_dict = WebHook.from_dict(web_hook_dict)
+```
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+