Voucher: Add creation date (Z#23202621) (#5359)

* Voucher: Add creation date (Z#23202621)

* Migration fix

* Update doc/api/resources/vouchers.rst

Co-authored-by: luelista <weller@rami.io>

* Update src/pretix/base/migrations/0285_voucher_created.py

Co-authored-by: luelista <weller@rami.io>

---------

Co-authored-by: luelista <weller@rami.io>

src/pretix/base/migrations/0285_voucher_created.py

@@ -0,0 +1,46 @@
+# Generated by Django 4.2.16 on 2025-08-08 09:13
+
+from django.db import migrations, models
+from django.db.models import Min
+from django.utils.timezone import now
+
+
+def backfill_voucher_created(apps, schema_editor):
+    Voucher = apps.get_model("pretixbase", "Voucher")
+    LogEntry = apps.get_model("pretixbase", "LogEntry")
+    ContentType = apps.get_model("contenttypes", "ContentType")
+    ct = None
+
+    for v in Voucher.objects.filter(created__isnull=True).iterator():
+        if not ct:
+            # "Lazy-loading" to prevent this to be executed on new DBs where the content type does not yet
+            # exist -- but also no vouchers do
+            ct = ContentType.objects.get(app_label='pretixbase', model='voucher')
+        v.created = LogEntry.objects.filter(
+            content_type=ct,
+            object_id=v.pk,
+        ).aggregate(m=Min("datetime"))["m"] or now()
+        v.save(update_fields=["created"])
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("pretixbase", "0284_ordersyncresult_ordersyncqueue"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="voucher",
+            name="created",
+            field=models.DateTimeField(auto_now_add=True, null=True),
+        ),
+        migrations.RunPython(
+            backfill_voucher_created,
+            migrations.RunPython.noop,
+        ),
+        migrations.AlterField(
+            model_name="voucher",
+            name="created",
+            field=models.DateTimeField(auto_now_add=True),
+        ),
+    ]

src/pretix/base/models/vouchers.py

@@ -174,6 +174,9 @@ class Voucher(LoggedModel):
         ('percent', _('Reduce product price by (%)')),
     )
 
+    created = models.DateTimeField(
+        auto_now_add=True,
+    )
     event = models.ForeignKey(
         Event,
         on_delete=models.CASCADE,