* Feature: added a dummy Google Sheet, the expected schema, and a test to compare them.
* Feature: cleaned up GitHub Action for style checks and added PyTest.
* Feature: added support for storing Google API credentials in an environmental variable, and added it to
GitHub Actions.
* Feature: added check for Google Sheet ID.
* Feature: updated cached_property with property lru_cache to support Python 3.7.
* Bug: updated CCDH Terminology API endpoint for enumerations.
* Bug: fixed code to correctly handle 404 responses from the TCCM Terminology Service.
* Bug: replaced unnecessary print() in GSheetModel with logging.error().