Store whether we know email addresses are working because links have been clicked

src/pretix/base/migrations/0121_order_email_known_to_work.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.1 on 2019-05-15 05:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0120_auto_20190509_0736'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='order',
+            name='email_known_to_work',
+            field=models.BooleanField(default=False),
+        ),
+    ]