* When an RPC is rejected because it's RPC-unsafe say why in the error message

* Make wildcard storage change subscriptions RPC-unsafe

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Fix typo

* Fix tests

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>