credentials_file: Path to a JSON file containing the credentials and key used to subscribe. As an alternative you can use the credentials_json config option or rely on Google Application Default Credentials.
credentials_json: JSON blob containing the credentials and key used to subscribe. This can be as an alternative to credentials_file if you want to embed the credential data within your config file or put the information into a keystore. You may also use Google Application Default Credentials.
Events are published in gzip compressed json lines format.