Now that richtext has been extracted (EZP-28009), the code in ezpublish-kernel that got moved needs to be marked as extracted. The list of affected files can be found in ezsystems/ezpublish-kernel#2289.

Deprecation warnings should be added for elements that may be used by developers. But we must keep in mind that since the richtext services are not removed, the classes still get instanciated, and may trigger deprecation warnings even if developers don't use it.