add multi collections (#315)

* start to add multi-collections

* create multi collection with no items

* edit multi collections

* fix plex credentials threading issue

* add playback order to multi collection items

* group episodes outside of shuffled enumerator

* move playback order onto each schedule item

* fix multi collection grouping

* update changelog

ErsatzTV.Application/ProgramSchedules/ProgramScheduleViewModel.cs

@@ -1,11 +1,8 @@
-using ErsatzTV.Core.Domain;
-
-namespace ErsatzTV.Application.ProgramSchedules
+namespace ErsatzTV.Application.ProgramSchedules
 {
     public record ProgramScheduleViewModel(
         int Id,
         string Name,
-        PlaybackOrder MediaCollectionPlaybackOrder,
         bool KeepMultiPartEpisodesTogether,
         bool TreatCollectionsAsShows);
 }