Bugs encountered:
Once the dialog pops up, filling in the subject and pressing RETURN
doesn't work. It fails to read the subject. The primary button needs to
be clicked on. This is a generic issue, not related to this PR
Behaviour:
-[x] Add button on communication to split thread
-[x] Popup asks for new subject
-[x] Copy "Customer", "Sender" and other relevant fields to this issue
-[x] Move thread and replies to new issue
fixes#14600
769054e00d