Default sorts should be in the domain

domain/mediafile.go

@@ -33,6 +33,11 @@ func (mf *MediaFile) ContentType() string {
 }
 
 type MediaFiles []MediaFile
+func (a MediaFiles) Len() int { return len(a) }
+func (a MediaFiles) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+func (a MediaFiles) Less(i, j int) bool {
+	return (a[i].DiscNumber * 1000 + a[i].TrackNumber) < (a[j].DiscNumber * 1000 + a[j].TrackNumber)
+}
 
 type MediaFileRepository interface {
 	BaseRepository