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.

duty_teller.egg-info/requires.txt

@@ -10,6 +10,7 @@ icalendar<6.0,>=5.0
 [dev]
 pytest<9.0,>=8.0
 pytest-asyncio<1.0,>=0.24
+pytest-cov<7.0,>=6.0
 httpx<1.0,>=0.27
 
 [docs]