Google Authentication does not detect IAM service accounts

The current code to guess what authentication mode is being used assumes that all services accounts end in 'developer.gserviceaccount.com' but that is no longer true for service accounts that use IAM. Those accounts end with '@<project-name>.iam.gserviceaccount.com'

https://cloud.google.com/iam/docs/service-accounts#product_name_short_service_accounts

The current authentication will not work for these service accounts and the library will fallback to an installed application auth flow (which prompts for user input to do out of band OAuth)

Relevant Commit: 3849f65fe5289f7d7160b7537afa930c7e2ea8a8