Function grant 

pub(crate) fn grant(
    api: &str,
    auth: AuthOptions<'_>,
    id: &str,
    repo: &str,
    level: &str,
) -> !

choir grant <api> <request-id> <owner/repo> [read|write]

Nothing to send afterwards, and that is the point: the request becomes an invite under the id and secret the asker already holds, so the link they were given is the link that starts working.