Dialogs are unnecessarily loading data/submitting data

• Absence reasons
• Detail page for person submits mutation without changes on opening

added part::frontend type::bug labels

assigned to @yuha

created branch 298-dialogs-are-unnecessarily-loading-data-submitting-data to address this issue

mentioned in merge request !383 (merged)

added source::customer::kath label

closed with merge request !383 (merged)

mentioned in commit 6578adf5

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