Small clean up to remove the explicit support for copying extendedfrom

in the new meeting editor - extendedfrom's have not been in use for
years, and the new UI doesn't support making them (one should just
make another session instead or modify the timeslot, which is now
possible to do individually).
 - Legacy-Id: 18438

Author: OleLaursen

ietf/meeting/views.py

@@ -435,27 +435,13 @@ def new_meeting_schedule(request, num, owner=None, name=None):
             new_schedule.save()
 
             if schedule:
-                # keep a mapping so that extendedfrom references can be chased
-                old_pk_to_new_pk = {}
-                extendedfroms = {}
                 for assignment in schedule.assignments.all():
-                    extendedfrom_id = assignment.extendedfrom_id
-
                     # clone by resetting primary key
-                    old_pk = assignment.pk
                     assignment.pk = None
                     assignment.schedule = new_schedule
                     assignment.extendedfrom = None
                     assignment.save()
 
-                    old_pk_to_new_pk[old_pk] = assignment.pk
-                    if extendedfrom_id is not None:
-                        extendedfroms[assignment.pk] = extendedfrom_id
-
-                for pk, extendedfrom_id in extendedfroms.values():
-                    if extendedfrom_id in old_pk_to_new_pk:
-                        SchedTimeSessAssignment.objects.filter(pk=pk).update(extendedfrom=old_pk_to_new_pk[extendedfrom_id])
-
             # now redirect to this new schedule
             return redirect(edit_meeting_schedule, meeting.number, new_schedule.owner_email(), new_schedule.name)