Remove unique-together requirement for BomItem model (#3104)

* Remove unique-together requirement for BomItem model

Ref: https://github.com/inventree/InvenTree/issues/1254

* Update unit test

* Remove unused import

InvenTree/build/test_build.py

@@ -3,7 +3,6 @@
 from django.test import TestCase
 
 from django.core.exceptions import ValidationError
-from django.db.utils import IntegrityError
 
 from InvenTree import status_codes as status
 
@@ -194,14 +193,13 @@ class BuildTest(BuildTestBase):
         b.save()
 
     def test_duplicate_bom_line(self):
-        # Try to add a duplicate BOM item - it should fail!
+        # Try to add a duplicate BOM item - it should be allowed
 
-        with self.assertRaises(IntegrityError):
-            BomItem.objects.create(
-                part=self.assembly,
-                sub_part=self.sub_part_1,
-                quantity=99
-            )
+        BomItem.objects.create(
+            part=self.assembly,
+            sub_part=self.sub_part_1,
+            quantity=99
+        )
 
     def allocate_stock(self, output, allocations):
         """

InvenTree/part/migrations/0077_alter_bomitem_unique_together.py

@@ -0,0 +1,17 @@
+# Generated by Django 3.2.13 on 2022-05-31 01:42
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0076_auto_20220516_0819'),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name='bomitem',
+            unique_together=set(),
+        ),
+    ]

InvenTree/part/models.py

@@ -2899,9 +2899,6 @@ class BomItem(models.Model, DataImportMixin):
     class Meta:
         verbose_name = _("BOM Item")
 
-        # Prevent duplication of parent/child rows
-        unique_together = ('part', 'sub_part')
-
     def __str__(self):
         return "{n} x {child} to make {parent}".format(
             parent=self.part.full_name,