Subscription handling of plugins / endpoints #1106
Description
Plugins (Endpoints / class extenders) can have query parameters. For example, the /search endpoint. The problem of this, is that the front-end tries to subscribe to every single ?query-param, but these resources don't exist in the DB.
However, it's entirely possible that people make plugins / endpoints that do implement some form of custom subscription handler.
Our Chat class extender, for example, already has some custom logic. Right now we do that through a CommitHandler, but maybe we can do something like a true SubscriptionHandler?