Add 'from_service_account_info' classmethod factory to clients. #705
Description
Follow-on to #244.
See discussion in googleapis/python-cloud-core#8
The rationale is that some users prefer not to store service account credentials on the filesystem, but instead pass them in via e.g. the environment.
@classmethod
def from_service_account_file(cls, info: dict, *args, **kwargs):
"""Creates an instance of this client using the provided credentials info.
Args:
info (dict): The service account private key info.
args: Additional arguments to pass to the constructor.
kwargs: Additional arguments to pass to the constructor.
Returns:
{@api.name}: The constructed client.
"""
credentials = service_account.Credentials.from_service_account_info(info)
kwargs["credentials"] = credentials
return cls(*args, **kwargs)