fix: correct serialization of fields

program/serializers.py

@@ -1475,14 +1475,23 @@ class ApplicationStatePurgeSerializer(serializers.Serializer):
 class PlaylistSerializer(serializers.ModelSerializer):
     class PlaylistEntrySerializer(serializers.ModelSerializer):
         class Meta:
+            extra_kwargs = {
+                "line_num": {"write_only": True},
+            }
             model = PlaylistEntry
             fields = (
                 "duration",
                 "file_id",
+                "line_num",
                 "uri",
             )
 
-    entries = PlaylistEntrySerializer(many=True)
+    entries = PlaylistEntrySerializer(many=True, required=False)
+    show_id = serializers.PrimaryKeyRelatedField(
+        queryset=Show.objects.all(),
+        required=True,
+        source="show",
+    )
 
     class Meta:
         model = Playlist