Fix a CASCADE on shops

ram/roster/migrations/0035_alter_rollingstock_shop.py

@@ -0,0 +1,25 @@
+# Generated by Django 5.1.4 on 2025-01-27 22:21
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("metadata", "0023_shop"),
+        ("roster", "0034_rollingstock_shop"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="rollingstock",
+            name="shop",
+            field=models.ForeignKey(
+                blank=True,
+                null=True,
+                on_delete=django.db.models.deletion.SET_NULL,
+                to="metadata.shop",
+            ),
+        ),
+    ]

ram/roster/models.py

@@ -104,7 +104,7 @@ class RollingStock(BaseModel):
     )
     production_year = models.SmallIntegerField(null=True, blank=True)
     shop = models.ForeignKey(
-        Shop, on_delete=models.CASCADE, null=True, blank=True
+        Shop, on_delete=models.SET_NULL, null=True, blank=True
     )
     purchase_date = models.DateField(null=True, blank=True)
     price = models.DecimalField(