Auto-check-in for specific sales channels (#1409)

* Autocheckin data model/cosmetics

* Expose automatically checked-in OrderPositions

* Expose automatically checked-in OrderPositions in CSV/PDF Exports

* Fix some tests, try to fix MultiStringField/CheckboxSelectMultiple

* Actually fix MultiStringField/CheckboxSelectMultiple.
(Not pretty, but it works)

* Fix more tests

* Squash migration

* Also fix CSV/nameparts-test

* Changes for Autocheckin code-review

* Perform Auto-Checkins through new core plugin

* Update config-doc to reflect also checkinlists

* Explicitly output AutoCheckin Yes/No for CSV-Export (+ fix test)

* Move autocheckin from plugin to service

* API-doc

* Fix API-doc spelling

* Checkinlist-API and autocheckin order tests

* Performance improvement when reading checkinlists for autocheckin

Co-Authored-By: Raphael Michel <michel@rami.io>

* Autocheckin test for order created through API

* Resolve migration conflict

src/pretix/control/forms/checkin.py

@@ -5,6 +5,7 @@ from django_scopes.forms import (
     SafeModelChoiceField, SafeModelMultipleChoiceField,
 )
 
+from pretix.base.channels import get_all_sales_channels
 from pretix.base.models.checkin import CheckinList
 from pretix.control.forms.widgets import Select2
 
@@ -15,6 +16,16 @@ class CheckinListForm(forms.ModelForm):
         kwargs.pop('locales', None)
         super().__init__(**kwargs)
         self.fields['limit_products'].queryset = self.event.items.all()
+        self.fields['auto_checkin_sales_channels'] = forms.MultipleChoiceField(
+            label=self.fields['auto_checkin_sales_channels'].label,
+            help_text=self.fields['auto_checkin_sales_channels'].help_text,
+            required=self.fields['auto_checkin_sales_channels'].required,
+            choices=(
+                (c.identifier, c.verbose_name) for c in get_all_sales_channels().values()
+            ),
+            widget=forms.CheckboxSelectMultiple
+        )
+
         if self.event.has_subevents:
             self.fields['subevent'].queryset = self.event.subevents.all()
             self.fields['subevent'].widget = Select2(
@@ -40,12 +51,14 @@ class CheckinListForm(forms.ModelForm):
             'all_products',
             'limit_products',
             'subevent',
-            'include_pending'
+            'include_pending',
+            'auto_checkin_sales_channels'
         ]
         widgets = {
             'limit_products': forms.CheckboxSelectMultiple(attrs={
                 'data-inverse-dependency': '<[name$=all_products]'
             }),
+            'auto_checkin_sales_channels': forms.CheckboxSelectMultiple()
         }
         field_classes = {
             'limit_products': SafeModelMultipleChoiceField,