These changes will make use of the official `google-api-python-client`
library instead of relying on manual HTTP requests.

Therer are two main advantages of these changes:

- the Tap doesn't need to worry about the Google API interaction
  details as its hidden away by the Google official lib.
- We can use the authentication helpers from the lib to ease the
  credentials management for the user. In that way the current PR
  implements two auth mean: installed OAuth client authentication or
  Service Accounts authentication.

The only downside of this change is that it breaks the current
`config.json` parameters for existing users.