Beacon OAuth Rest Service
Beacon's OAuth 2.0 token service, implementing the refresh_token grant and linking to https://oauth.net/2/grant-types/refresh-token/ in its own description. Returns access_token, token_type, expires_in, refresh_expires_in, refresh_token and scope. The scopes request field is a refresh-behaviour selector (empty, "all" or "refresh_token"), not a permission scope. No initial grant is published — the first refresh_token is issued during partner onboarding. This is the only Beacon document that declares a servers[] block, and its default is the UAT host.