The RegisteredClient to use on the cache fast-path. The client_id is
read from the persisted token (so DCR/CIMD users, who have no statically
configured client_id, still carry the AS-issued one needed to refresh),
falling back to the configured opts.clientId for records that predate
persisting it. The secret comes from opts (it is not persisted).
The RegisteredClient to use on the cache fast-path. The client_id is read from the persisted token (so DCR/CIMD users, who have no statically configured client_id, still carry the AS-issued one needed to refresh), falling back to the configured opts.clientId for records that predate persisting it. The secret comes from opts (it is not persisted).