Invoices: Visibly mark paid invoices (#3094)

src/pretix/base/migrations/0229_invoice_payment_provider_stamp.py

@@ -0,0 +1,19 @@
+# Generated by Django 3.2.17 on 2023-02-07 10:00
+
+import django.core.serializers.json
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0228_scheduledeventexport_scheduledorganizerexport'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='invoice',
+            name='payment_provider_stamp',
+            field=models.CharField(max_length=100, null=True),
+        ),
+    ]