ReadonlyaccessReadonlyexpiresEpoch milliseconds; derived from the token response's expires_in.
Optional ReadonlyrefreshAbsent when the provider issued a non-refreshable (or already-expired single-use) access token; callers must treat re-authentication as the only recovery path in that case.
Optional ReadonlyscopeOptional Readonlytoken
One access/refresh token pair, as persisted between requests.