mod_http_oauth2: Validate consistency of response and grant types Ensure that these correlated fields make sense per RFC 7591 § 2.1, even though we currently only check the response type during authorization. This could probably all be deleted if (when!) we remove the implicit grant, since then these things don't make any sense anymore.

This module discards typing notifications sent to a bare host JID,
preventing error replies to be sent. These errors are harmless but can
be annoying sometimes if your client shows them prominently.