offline_access returning invalid_scope error

I'm working with the [lightroom api](https://www.adobe.io/apis/creativecloud/lightroom/apidocs.html#!docs/api/LightroomPartnerAPIsSpec.json) and trying to get a refreshable token so the user doesn't need to login every 24 hours.

When I hit `ims/authorize/v2` and request the scopes `openid,lr_partner_apis,offline_access`, the callback returns an `invalid_scope` error, even though offline_access is a [valid scope](https://www.adobe.io/authentication/auth-methods.html#!AdobeDocs/adobeio-auth/master/OAuth/Scopes.md#identity-scopes) listed in the docs.

Start with the `ims/authorize/v2` entry point and compare the requested `openid`, `lr_partner_apis`, and `offline_access` scopes against the linked authentication and Lightroom API documentation. Determine whether the documentation or the endpoint behavior is inconsistent; done means the supported scope behavior and required guidance are clearly documented.

Written by the indexing model from the issue text.