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/sync/docs/DocumentAddress.md

@@ -0,0 +1,42 @@
+# DocumentAddress
+
+This information comes from the customer which can be set with customer_id.
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**salutation** | **int** | 0: empty<br/> 1: Herrn<br/> 2: Frau<br/> 3: Firma<br/> 4: Herrn und Frau<br/> 5: Eheleute<br/> 6: Familie | [optional] [readonly] 
+**personal** | **bool** |  | [optional] [readonly] 
+**title** | **str** |  | [optional] [readonly] 
+**first_name** | **str** |  | [optional] [readonly] 
+**last_name** | **str** |  | [optional] [readonly] 
+**suffix_1** | **str** |  | [optional] [readonly] 
+**suffix_2** | **str** |  | [optional] [readonly] 
+**company_name** | **str** |  | [optional] [readonly] 
+**street** | **str** |  | [optional] [readonly] 
+**zip_code** | **str** |  | [optional] [readonly] 
+**city** | **str** |  | [optional] [readonly] 
+**state** | **str** |  | [optional] [readonly] 
+**country** | **str** |  | [optional] [readonly] 
+
+## Example
+
+```python
+from easybill_generated_sync.models.document_address import DocumentAddress
+
+# TODO update the JSON string below
+json = "{}"
+# create an instance of DocumentAddress from a JSON string
+document_address_instance = DocumentAddress.from_json(json)
+# print the JSON string representation of the object
+print(DocumentAddress.to_json())
+
+# convert the object into a dict
+document_address_dict = document_address_instance.to_dict()
+# create an instance of DocumentAddress from a dict
+document_address_from_dict = DocumentAddress.from_dict(document_address_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)
+
+