code: def mark_thread_as_read(self, request, pk=None):
          
          # we get the thread and check for permission
          thread = Thread.objects.get(id=pk)
          self.check_object_permissions(request, thread)
          # we save the date
          try:
              participation = Participation.objects.get(thread=thread, participant=request.rest_messaging_participant)
              participation.date_last_check = now()
              participation.save()
              # we return the thread
              serializer = self.get_serializer(thread)
              return Response(serializer.data)
          except Exception:
              return Response(status=status.HTTP_400_BAD_REQUEST)
docs: Pk is the pk of the Thread to which the messages belong.