Refs #39 -- New concept of "teams" (#478)

* New models

* CRUD UI

* UI for adding/removing team members

* Log display for teams

* Fix invitations, move frontend

* Drop old models (incomplete)

* Drop more old stuff

* Drop even more old stuff

* Fix tests

* Fix permission test

* flake8 fix

* Add tests fore the new code

* Rebase migrations

src/pretix/control/forms/organizer.py

@@ -1,8 +1,9 @@
 from django import forms
+from django.core.exceptions import ValidationError
 from django.utils.translation import ugettext_lazy as _
 
 from pretix.base.forms import I18nModelForm
-from pretix.base.models import Organizer
+from pretix.base.models import Organizer, Team
 from pretix.multidomain.models import KnownDomain
 
 
@@ -65,3 +66,35 @@ class OrganizerUpdateForm(OrganizerForm):
             instance.get_cache().clear()
 
         return instance
+
+
+class TeamForm(forms.ModelForm):
+
+    def __init__(self, *args, **kwargs):
+        organizer = kwargs.pop('organizer')
+        super().__init__(*args, **kwargs)
+        self.fields['limit_events'].queryset = organizer.events.all()
+
+    class Meta:
+        model = Team
+        fields = ['name', 'all_events', 'limit_events', 'can_create_events',
+                  'can_change_teams', 'can_change_organizer_settings',
+                  'can_change_event_settings', 'can_change_items',
+                  'can_view_orders', 'can_change_orders',
+                  'can_view_vouchers', 'can_change_vouchers']
+        widgets = {
+            'limit_events': forms.CheckboxSelectMultiple(attrs={
+                'data-inverse-dependency': '#id_all_events'
+            }),
+        }
+
+    def clean(self):
+        data = super().clean()
+        if self.instance.pk and not data['can_change_teams']:
+            if not self.instance.organizer.teams.exclude(pk=self.instance.pk).filter(
+                can_change_teams=True, members__isnull=False
+            ).exists():
+                raise ValidationError(_('The changes could not be saved because there would be no remaining team with '
+                                        'the permission to change teams and permissions.'))
+
+        return data