Fix #630 -- manual check-in of attendees (#642)

* [WIP] manual check-in of attendees

This enables manual check-in of attendees.  The post-code was heavily
copied from the APIRedeemView of the pretixdroid, thus so far this seems
to be working, but I have a few questions:

The checkin-Objects generated by the pretixdroid-app have a nonce.
Should the checkin object generated here have a nonce, too?

Should the result of the check-in be noted in any other way than by the
change of the status?

* addressed review comments

* implement unit test for manual checkin

* fix style-issues

* Slight layout change

* Log who did the manual check-in

* Improve unit test to check the result of the action

src/pretix/control/views/checkin.py

@@ -1,8 +1,13 @@
+from django.contrib import messages
+from django.core.urlresolvers import reverse
 from django.db.models import F, Prefetch, Q
 from django.db.models.functions import Coalesce
+from django.shortcuts import redirect
+from django.utils.timezone import now
+from django.utils.translation import ugettext_lazy as _
 from django.views.generic import ListView
 
-from pretix.base.models import Checkin, Item, OrderPosition
+from pretix.base.models import Checkin, Item, Order, OrderPosition
 from pretix.control.permissions import EventPermissionRequiredMixin
 
 
@@ -69,6 +74,31 @@ class CheckInView(EventPermissionRequiredMixin, ListView):
                            or "subevent" in self.request.GET)
         return ctx
 
+    def post(self, request, *args, **kwargs):
+        positions = OrderPosition.objects.select_related('item', 'variation', 'order', 'addon_to').filter(
+            order__event=self.request.event,
+            pk__in=request.POST.getlist('checkin')
+        )
+
+        for op in positions:
+            created = False
+            if op.order.status == Order.STATUS_PAID:
+                ci, created = Checkin.objects.get_or_create(position=op, defaults={
+                    'datetime': now(),
+                })
+            op.order.log_action('pretix.control.views.checkin', data={
+                'position': op.id,
+                'positionid': op.positionid,
+                'first': created,
+                'datetime': now()
+            }, user=request.user)
+
+        messages.success(request, _('The selected tickets have been marked as checked in.'))
+        return redirect(reverse('control:event.orders.checkins', kwargs={
+            'event': self.request.event.slug,
+            'organizer': self.request.event.organizer.slug
+        }) + '?' + request.GET.urlencode())
+
     @staticmethod
     def get_ordering_keys_mappings():
         return {