Add constraint for a maximum number of a ticket per order

src/pretix/base/migrations/0052_auto_20170324_1506.py

@@ -0,0 +1,38 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.6 on 2017-03-24 15:06
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0051_auto_20170206_2027'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='invoice',
+            options={'ordering': ('invoice_no',)},
+        ),
+        migrations.AlterModelOptions(
+            name='orderposition',
+            options={'ordering': ('positionid', 'id'), 'verbose_name': 'Order position', 'verbose_name_plural': 'Order positions'},
+        ),
+        migrations.AddField(
+            model_name='item',
+            name='max_per_order',
+            field=models.IntegerField(blank=True, help_text='This product can only be bought at most this times within one order. If you keep the field empty or set it to 0, there is no special limit for this product. The limit for the maximum number of items in the whole order applies regardless.', null=True, verbose_name='Maximum times per order'),
+        ),
+        migrations.AlterField(
+            model_name='item',
+            name='allow_cancel',
+            field=models.BooleanField(default=True, help_text='If this is active and the general event settings allo wit, orders containing this product can be canceled by the user until the order is paid for. Users cannot cancel paid orders on their own and you can cancel orders at all times, regardless of this setting', verbose_name='Allow product to be canceled'),
+        ),
+        migrations.AlterField(
+            model_name='item',
+            name='default_price',
+            field=models.DecimalField(decimal_places=2, help_text='If this product has multiple variations, you can set different prices for each of the variations. If a variation does not have a special price or if you do not have variations, this price will be used.', max_digits=7, null=True, verbose_name='Default price'),
+        ),
+    ]