chore: add coverage reporting and improve documentation

- Added `pytest-cov` as a development dependency for coverage reporting.
- Configured pytest to include coverage options, ensuring code coverage is reported and enforced.
- Updated the README to include contributing guidelines and logging policies, enhancing clarity for developers.
- Added a new section in the configuration documentation emphasizing the necessity of serving the application over HTTPS in production for security purposes.
- Introduced a new `.coverage` file to track test coverage metrics.

pyproject.toml

@@ -26,6 +26,7 @@ duty-teller = "duty_teller.run:main"
 dev = [
     "pytest>=8.0,<9.0",
     "pytest-asyncio>=0.24,<1.0",
+    "pytest-cov>=6.0,<7.0",
     "httpx>=0.27,<1.0",
 ]
 docs = [
@@ -47,5 +48,9 @@ version_path_separator = "os"
 line-length = 120
 target-version = ["py311"]
 
+[tool.pytest.ini_options]
+addopts = "--cov=duty_teller --cov-report=term-missing --cov-fail-under=51"
+asyncio_mode = "auto"
+
 [tool.pylint.messages_control]
 disable = ["C0114", "C0115", "C0116"]