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/PDFTemplate.md

@@ -0,0 +1,33 @@
+# PDFTemplate
+
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**id** | **str** |  | [optional] [default to 'INVOICE-DE']
+**name** | **str** |  | [optional] [default to 'Default template']
+**pdf_template** | **str** |  | [optional] [default to 'DE']
+**document_type** | **str** |  | [optional] [default to 'INVOICE']
+**settings** | [**PDFTemplateSettings**](PDFTemplateSettings.md) |  | [optional] 
+
+## Example
+
+```python
+from easybill_generated_async.models.pdf_template import PDFTemplate
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of PDFTemplate from a JSON string
+pdf_template_instance = PDFTemplate.from_json(json)
+# print the JSON string representation of the object
+print(PDFTemplate.to_json())
+
+# convert the object into a dict
+pdf_template_dict = pdf_template_instance.to_dict()
+# create an instance of PDFTemplate from a dict
+pdf_template_from_dict = PDFTemplate.from_dict(pdf_template_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)
+
+