refactor: Directory module's functions into class

[gcharest]

Summary | Résumé

Summary | Résumé

Refactored the Google Next Directory module as a helper class.

• Google Directory is now a class
• State is preserved so the authenticated service can be created once and used multiple times before being closed
• Clarified use of these helper classes: the hoisted methods make it easy to use through the code base but it is possible to simply use the Service's get_google_service and use the regular approach described in the documentation