public function createAction(
        string $production_slug,
        AuthorizationCheckerInterface $auth,
        TokenStorageInterface $token,
        Request $request
    ): Response {
        // Lookup the production by production_slug.
        $production_repo = $this->em->getRepository(Production::class);
        if (null === $production = $production_repo->findOneBy(['slug' => $production_slug])) {
            throw new NotFoundHttpException();
        }

        // Check permissions for this action, must be an editor or better.
        if (!$auth->isGranted('GROUP_ROLE_EDITOR', $production)) {
            throw new AccessDeniedException();
        }

        // Create new schedule in this production.
        $schedule = new Schedule();
        $schedule->setActive(true);
        $schedule->addGroup($production);
        $schedule->setAuthor($token->getToken()->getUser()->getUsername());

        // Create a form for this schedule and handle it.
        $form = $this->form->create(ScheduleType::class, $schedule);
        $form->handleRequest($request);

        // Form is submitted and valid.
        if ($form->isSubmitted() && $form->isValid()) {
            // Match events with schedule.
            foreach ($schedule->getEvents() as $event) {
                foreach ($schedule->getGroups() as $group) {
                    if (!$event->hasGroup($group)) {
                        $event->addGroup($group);
                    }
                }
                $event->setColour($schedule->getColour());
                $event->setLocation($schedule->getLocation());
                $event->setActive($schedule->isActive());
                $event->setAuthor($schedule->getAuthor());
            }

            // Persist the schedule (will cascade persist).
            $this->em->persist($schedule);
            $this->em->flush();

            // Set success message and redirect.
            $this->session->getFlashBag()->add(
                'success',
                $this->translator->trans('schedule.created', [
                    '%schedule%' => $schedule->getName(),
                ], BkstgScheduleBundle::TRANSLATION_DOMAIN)
            );

            return new RedirectResponse($this->url_generator->generate(
                'bkstg_schedule_read',
                [
                    'id' => $schedule->getId(),
                    'production_slug' => $production->getSlug(),
                ]
            ));
        }

        // Render the form.
        return new Response($this->templating->render('@BkstgSchedule/Schedule/create.html.twig', [
            'form' => $form->createView(),
            'production' => $production,
        ]));
    }