Do we need `optReference` here and in other cases? Might be better to use `reference` instead, since it should always have a group assigned https://github.com/JeroenoBoy/scrumdapp/blob/6a91493c2ca6c688c08cf8002ab909643a93c9f3/src/main/kotlin/scrumdapp/models/GroupsTable.kt#L33-L34
Do we need
optReferencehere and in other cases? Might be better to usereferenceinstead, since it should always have a group assignedhttps://github.com/JeroenoBoy/scrumdapp/blob/6a91493c2ca6c688c08cf8002ab909643a93c9f3/src/main/kotlin/scrumdapp/models/GroupsTable.kt#L33-L34