Make subject editable in new course book

added part::backend part::frontend type::feature labels

assigned to @yuha

added source::customer::hns label

changed milestone to /AlekSIS%"[NLnet #3] Test and review with pilot schools"

created branch 275-make-subject-editable-in-new-course-book to address this issue

mentioned in merge request !369 (merged)

closed with merge request !369 (merged)

mentioned in commit 79962595