oauth_app_from_json() is being replaced with
gargle_oauth_client_from_json(), in light of the new
gargle_oauth_client class. Now oauth_app_from_json() potentially warns
about this deprecation and immediately passes its inputs through to
gargle_oauth_client_from_json().
gargle_app() is being replaced with gargle_client().
Arguments
- path
 JSON downloaded from Google Cloud Console, containing a client id and secret, in one of the forms supported for the
txtargument ofjsonlite::fromJSON()(typically, a file path or JSON string).- appname
 name of the application. This is not used for OAuth, but is used to make it easier to identify different applications.