[A11y] Cart renewal (#5109)

Allow customers to extend their cart reservation up to 11 times the configured reservation time

src/pretix/base/migrations/0280_cartposition_max_extend.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.20 on 2025-05-14 14:58
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0279_discount_event_date_from_discount_event_date_until'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='cartposition',
+            name='max_extend',
+            field=models.DateTimeField(null=True),
+        ),
+    ]