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/easybill_generated_async/models/text_template.py

@@ -0,0 +1,98 @@
+# coding: utf-8
+
+"""
+    easybill REST API
+
+     The first version of the easybill REST API. [CHANGELOG](https://api.easybill.de/rest/v1/CHANGELOG.md)  ## Authentication  You can choose between two available methods: `Basic Auth` or `Bearer Token`.  In each HTTP request, one of the following HTTP headers is required:  ``` # Basic Auth Authorization: Basic base64_encode('<email>:<api_key>') # Bearer Token Authorization: Bearer <api_key> ```  ## Limitations  ### Request Limit  * PLUS: 10 requests per minute * BUSINESS: 60 requests per minute  If the limit is exceeded, you will receive the HTTP error: `429 Too Many Requests`  ### Result Limit  All result lists are limited to 100 by default. This limit can be increased by the query parameter `limit` to a maximum of 1000.  ## Query filter  Many list resources can be filtered. In `/documents` you can filter e.g. by number with `/documents?number=111028654`. If you want to filter multiple numbers, you can either enter them separated by commas `/documents?number=111028654,222006895` or as an array `/documents?number[]=111028654&number[]=222006895`.  **Warning**: The maximum size of an HTTP request line in bytes is 4094. If this limit is exceeded, you will receive the HTTP error: `414 Request-URI Too Large`  ### Escape commas in query  You can escape commans in query `name=Patrick\\, Peter` if you submit the header `X-Easybill-Escape: true` in your request.  ## Property login_id  This is the login of your admin or employee account.  ## Date and Date-Time format Please use the timezone `Europe/Berlin`. * **date** = *Y-m-d* = `2016-12-31` * **date-time** = *Y-m-d H:i:s* = `2016-12-31 03:13:37`  Date or datetime can be `null` because the attributes have been added later and the entry is older.
+
+    The version of the OpenAPI document: 1.96.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""  # noqa: E501
+
+
+from __future__ import annotations
+import pprint
+import re  # noqa: F401
+import json
+
+from pydantic import BaseModel, ConfigDict, Field, StrictBool, StrictInt, StrictStr
+from typing import Any, ClassVar, Dict, List, Optional
+from typing import Optional, Set
+from typing_extensions import Self
+from pydantic_core import to_jsonable_python
+
+class TextTemplate(BaseModel):
+    """
+    TextTemplate
+    """ # noqa: E501
+    can_modify: Optional[StrictBool] = Field(default=None, description="Deprecated, field is always true.")
+    id: Optional[StrictInt] = None
+    text: StrictStr
+    title: StrictStr
+    __properties: ClassVar[List[str]] = ["can_modify", "id", "text", "title"]
+
+    model_config = ConfigDict(
+        validate_by_name=True,
+        validate_by_alias=True,
+        validate_assignment=True,
+        protected_namespaces=(),
+    )
+
+
+    def to_str(self) -> str:
+        """Returns the string representation of the model using alias"""
+        return pprint.pformat(self.model_dump(by_alias=True))
+
+    def to_json(self) -> str:
+        """Returns the JSON representation of the model using alias"""
+        return json.dumps(to_jsonable_python(self.to_dict()))
+
+    @classmethod
+    def from_json(cls, json_str: str) -> Optional[Self]:
+        """Create an instance of TextTemplate from a JSON string"""
+        return cls.from_dict(json.loads(json_str))
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Return the dictionary representation of the model using alias.
+
+        This has the following differences from calling pydantic's
+        `self.model_dump(by_alias=True)`:
+
+        * `None` is only added to the output dict for nullable fields that
+          were set at model initialization. Other fields with value `None`
+          are ignored.
+        * OpenAPI `readOnly` fields are excluded.
+        * OpenAPI `readOnly` fields are excluded.
+        """
+        excluded_fields: Set[str] = set([
+            "can_modify",
+            "id",
+        ])
+
+        _dict = self.model_dump(
+            by_alias=True,
+            exclude=excluded_fields,
+            exclude_none=True,
+        )
+        return _dict
+
+    @classmethod
+    def from_dict(cls, obj: Optional[Dict[str, Any]]) -> Optional[Self]:
+        """Create an instance of TextTemplate from a dict"""
+        if obj is None:
+            return None
+
+        if not isinstance(obj, dict):
+            return cls.model_validate(obj)
+
+        _obj = cls.model_validate({
+            "can_modify": obj.get("can_modify"),
+            "id": obj.get("id"),
+            "text": obj.get("text"),
+            "title": obj.get("title")
+        })
+        return _obj
+
+