Improve history handling

Only store AK in database once all attributes are correctly set.
Previously, each AK was automatically edited directly after saving to add the link, which created two history entries for that AK.
This resolves #141.
Additionally, only display slots as (re-)scheduled when they are indeed scheduled (i.e., have a starting time stamp).

AKDashboard/views.py

@@ -54,7 +54,7 @@ class DashboardEventView(DetailView):
             # Changes in plan
             if apps.is_installed("AKPlan"):
                 if not context['event'].plan_hidden:
-                    last_changed_slots = AKSlot.objects.filter(event=context['event']).order_by('-updated')[
+                    last_changed_slots = AKSlot.objects.filter(event=context['event'], start__isnull=False).order_by('-updated')[
                                          :int(settings.DASHBOARD_RECENT_MAX)]
                     for changed_slot in last_changed_slots:
                         recent_changes.append({'icon': ('clock', 'far'),

AKSubmission/views.py

@@ -215,7 +215,8 @@ class AKAndAKWishSubmissionView(EventSlugMixin, EventInactiveRedirectMixin, Crea
             return redirect(reverse_lazy('submit:submission_overview',
                                          kwargs={'event_slug': form.cleaned_data["event"].slug}))
 
-        super_form_valid = super().form_valid(form)
+        # Generate object but don't store it in the database yet
+        self.object = form.save(commit=False)
 
         # Generate wiki link
         if form.cleaned_data["event"].base_url:
@@ -225,7 +226,9 @@ class AKAndAKWishSubmissionView(EventSlugMixin, EventInactiveRedirectMixin, Crea
             if len(link) > 200:
                 messages.add_message(self.request, messages.WARNING,
                     _("Due to technical reasons, the link you entered was truncated to a length of 200 characters"))
-        self.object.save()
+
+        # Try to save AK and get redirect URL
+        super_form_valid = super().form_valid(form)
 
         # Set tags (and generate them if necessary)
         for tag_name in form.cleaned_data["tag_names"]: