T7024 fix: implement attachment-based forwarding
Summary:
Implement attachment-based forwarding.
Some notes:
- loadAsDraft was removed in favor of new enum loadType in QML, and callback based generic programming in C++
Reviewers: cmollekopf
Tags: Kube
Maniphest Tasks: T7024
Differential Revision: https://phabricator.kde.org/D10676