The function looks for .httr-oauth in the working directory. If it doesn't find it, it expects an application ID and a secret.
If you want to remove the existing .httr-oauth, set remove_old_oauth to TRUE. By default, it is set to FALSE.
The function launches a browser to allow you to authorize the application
Character. ssl, basic, own_account_readonly, upload_and_manage_own_videos,
partner, and partner_audit.
Required. ssl and basic are basically interchangeable. Default is ssl.
token
path to file containing the token. If a path is given, the function will first try to read from it.
Default is .httr-oauth in the local directory.
So if there is such a file, the function will first try to read from it.