Import absences correctly

Original title: Show absent teachers in substitution plan

The header of the substitution plan shows 'affected teachers'. It would also be interesting to see which teachers are absnet.

added part::frontend label

changed the description

assigned to @hansegucker

added type::bug label

I found the broken part in AlekSIS-App-Untis, so I will move the issue.

moved from AlekSIS-App-Chronos#102 (moved)

changed title from Show absent teachers in substitution plan to Import absences correctly

changed the description

There is a broken enum comparison: AbsenceType.GROUP is compared with 100, for example, but it has to be AbsenceType.GROUP.value == 100. Fix will come soon.

created merge request !45 (merged) to address this issue

mentioned in merge request !45 (merged)

closed with merge request !45 (merged)

mentioned in commit d6197fa8