fix: cba_id should be part of the serialized representation

cba_id was always part of the serialized note representation through the
use of `fields = "__all__"``and shouldn’t be write-only.

program/serializers.py

@@ -453,7 +453,6 @@ class NoteSerializer(serializers.ModelSerializer):
     timeslot = serializers.PrimaryKeyRelatedField(queryset=TimeSlot.objects.all())
     host = serializers.PrimaryKeyRelatedField(queryset=Host.objects.all())
     thumbnails = serializers.SerializerMethodField()  # Read-only
-    cba_id = serializers.IntegerField(required=False, write_only=True)
 
     @staticmethod
     def get_thumbnails(note):