fix: support non-integer PKs in NotificationMessage (fixes UUID overflow) (#12162)

NotificationMessage.target_object_id and source_object_id were typed as
PositiveIntegerField, which overflows when the referenced model uses a
UUID primary key (e.g. MachineConfig). Django's GenericForeignKey stores
the PK as a string in the database, so the field type should be
CharField to accommodate any PK type (int, UUID, slug, etc.).

Changes:
- common/models.py: change target_object_id and source_object_id from
  PositiveIntegerField to CharField(max_length=255) on NotificationMessage
- common/migrations/0044: AlterField migration for both columns
- order/tests.py: update assertion from integer 1 to str(1) since
  CharField will now store the PK as a string

Fixes #12131

Signed-off-by: kaizeenn <khairil0153@gmail.com>

src/backend/InvenTree/common/migrations/0044_notificationmessage_charfield_pk.py

@@ -0,0 +1,29 @@
+"""Migration to change NotificationMessage object_id fields from PositiveIntegerField to CharField.
+
+This allows notifications to reference models that use non-integer primary keys,
+such as UUIDField (e.g. MachineConfig), without a database overflow error.
+
+See: https://github.com/inventree/InvenTree/issues/12131
+"""
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('common', '0043_auto_20260518_1206'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='notificationmessage',
+            name='target_object_id',
+            field=models.CharField(max_length=255),
+        ),
+        migrations.AlterField(
+            model_name='notificationmessage',
+            name='source_object_id',
+            field=models.CharField(max_length=255, null=True, blank=True),
+        ),
+    ]

src/backend/InvenTree/common/models.py

@@ -1678,7 +1678,7 @@ class NotificationMessage(models.Model):
         ContentType, on_delete=models.CASCADE, related_name='notification_target'
     )
 
-    target_object_id = models.PositiveIntegerField()
+    target_object_id = models.CharField(max_length=255)
 
     target_object = GenericForeignKey('target_content_type', 'target_object_id')
 
@@ -1691,7 +1691,7 @@ class NotificationMessage(models.Model):
         blank=True,
     )
 
-    source_object_id = models.PositiveIntegerField(null=True, blank=True)
+    source_object_id = models.CharField(max_length=255, null=True, blank=True)
 
     source_object = GenericForeignKey('source_content_type', 'source_object_id')
 

src/backend/InvenTree/order/tests.py

@@ -523,7 +523,7 @@ class OrderTest(ExchangeRateMixin, PluginRegistryMixin, TestCase):
 
             msg = messages.first()
 
-            self.assertEqual(msg.target_object_id, 1)
+            self.assertEqual(msg.target_object_id, str(1))
             self.assertEqual(msg.name, 'Overdue Purchase Order')
 
     def test_new_po_notification(self):