✅test(project): add mail_reader tests

fix unprecised typings replacing QuerySet type by list[Message] type, exclude test directory from mypy analysis and add tests for mail_reader.

pyproject.toml

@@ -31,3 +31,8 @@ packages = ["src/logwatcher"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
+
+[tool.mypy]
+exclude = [
+    "^tests/"
+]