Implement hidden_if_item_available_mode option (Z#23177008) (#4776)

This reverts commit b847612e1a.

src/pretix/base/migrations/0276_item_hidden_if_item_available_mode.py

@@ -13,6 +13,6 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name="item",
             name="hidden_if_item_available_mode",
-            field=models.CharField(default="hide", max_length=16),
+            field=models.CharField(default="hide", max_length=16, null=True),
         ),
     ]

src/pretix/base/migrations/0277_alter_item_hidden_if_item_available_mode.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.16 on 2025-01-24 12:38
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("pretixbase", "0276_item_hidden_if_item_available_mode"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="item",
+            name="hidden_if_item_available_mode",
+            field=models.CharField(default="hide", max_length=16),
+        ),
+    ]