As described in the manifest format doc, if the OAuth extension is installed the Manifest needs to provide its registration page URL, e.g. https://meta.wikimedia.org/wiki/Special:OAuthConsumerRegistration/propose.
Key name: see the spec
As per the spec, if OAuth is not installed then there should be no OAuth key in the output but this is to be addressed in a followup ticket
The OpenRefine team confirmed just the consumer proposal URL is all they need.