Moved getGroupMatches + Tests

lib/presentation/views/main_menu/group_view/create_group_view.dart

@@ -197,7 +197,7 @@ class _CreateGroupViewState extends State<CreateGroupView> {
   /// obsolete. For each such match, the group association is removed by setting
   /// its [groupId] to null.
   Future<void> deleteObsoleteMatchGroupRelations() async {
-    final groupMatches = await db.groupDao.getGroupMatches(
+    final groupMatches = await db.matchDao.getGroupMatches(
       groupId: widget.groupToEdit!.id,
     );
 

lib/presentation/views/main_menu/group_view/group_detail_view.dart

@@ -248,7 +248,7 @@ class _GroupDetailViewState extends State<GroupDetailView> {
   /// Loads statistics for this group
   Future<void> _loadStatistics() async {
     isLoading = true;
-    final groupMatches = await db.groupDao.getGroupMatches(groupId: _group.id);
+    final groupMatches = await db.matchDao.getGroupMatches(groupId: _group.id);
 
     setState(() {
       totalMatches = groupMatches.length;