17009 send email option

[``* `#17009` Extend work package PATCH endpoint to support optional notification``](https://community.openproject.org/work_packages/17009)
@hschink I know there are other places where we have added ad-hoc helper methods, but I really don't think this is the right place for this logic. IMO we should really move this into a service object (e.g. `UpdateWorkPackageService`) sooner rather than later.