Add missing class docstring to achieve 100% docstring coverage

- Add docstring to TestUtils class to complete 99.5% -> 100% coverage
- All functions and classes now have comprehensive docstrings

Author: dougollerenshaw

tests/test_utils.py

@@ -17,6 +17,8 @@
 
 
 class TestUtils(unittest.TestCase):
+    """Test cases for utility functions in aind_metadata_mapper.utils."""
+
     def test_ensure_timezone_none(self):
         """Test that ensure_timezone handles None input by returning current time with timezone.