As well as OAuth2 authentication, you can authenticate without user interaction via Service accounts. This involves downloading a secret JSON key with the authentication details.
To use, go to your Project in the https://console.developers.google.com/apis/credentials/serviceaccountkey
and select JSON Key type. Save the file
to your computer and call it via supplying
the file path to the json_file parameter.
Navigate to it via: Google Dev Console > Credentials > New credentials > Service account Key > Select service account > Key type = JSON
gar_auth_service(json_file,
scope = getOption("googleAuthR.scopes.selected"))the JSON file downloaded from Google Developer Console
Scope of the JSON file auth if needed
(Invisible) Sets authentication token
https://developers.google.com/identity/protocols/OAuth2ServiceAccount
https://developers.google.com/identity/protocols/OAuth2ServiceAccount
Other authentication functions: gar_attach_auto_auth,
gar_auth, gar_auto_auth,
gar_gce_auth,
get_google_token,
token_exists