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.

pyproject.toml

@@ -0,0 +1,30 @@
+[build-system]
+requires = ["hatchling>=1.27.0"]
+build-backend = "hatchling.build"
+
+[project]
+name = "easybill-client"
+version = "0.1.0"
+description = "Python easybill REST API client with Pydantic models and webhook helpers"
+readme = "README.md"
+requires-python = ">=3.11"
+authors = [
+  { name = "GitHub Copilot" }
+]
+dependencies = [
+  "httpx>=0.27,<1",
+  "pydantic>=2.8,<3",
+]
+
+[project.optional-dependencies]
+dev = [
+  "pytest>=8.3,<9",
+  "pytest-asyncio>=0.24,<1",
+]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+pythonpath = ["src"]
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/easybill_client"]