SupplierOrderLineItem gets reference to internal part

- For keeping track of how many of an internal part is on order!

InvenTree/supplier/migrations/0014_auto_20180417_1520.py

@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.12 on 2018-04-17 15:20
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0022_auto_20180417_0819'),
+        ('supplier', '0013_merge_20180417_1517'),
+    ]
+
+    operations = [
+        migrations.RenameField(
+            model_name='supplierorderlineitem',
+            old_name='part',
+            new_name='supplier_part',
+        ),
+        migrations.AddField(
+            model_name='supplierorderlineitem',
+            name='internal_part',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, to='part.Part'),
+        ),
+        migrations.AlterUniqueTogether(
+            name='supplierorderlineitem',
+            unique_together=set([('order', 'line_number'), ('order', 'internal_part'), ('order', 'supplier_part')]),
+        ),
+    ]

InvenTree/supplier/models.py

@@ -160,14 +160,17 @@ class SupplierOrderLineItem(models.Model):
     class Meta:
         unique_together = [
             ('order', 'line_number'),
-            ('order', 'part'),
+            ('order', 'supplier_part'),
+            ('order', 'internal_part'),
         ]
 
     order = models.ForeignKey(SupplierOrder, on_delete=models.CASCADE)
 
     line_number = models.PositiveIntegerField(default=1)
 
-    part = models.ForeignKey(SupplierPart, null=True, blank=True, on_delete=models.SET_NULL)
+    internal_part = models.ForeignKey(Part, null=True, blank=True, on_delete=models.SET_NULL)
+
+    supplier_part = models.ForeignKey(SupplierPart, null=True, blank=True, on_delete=models.SET_NULL)
 
     quantity = models.PositiveIntegerField(default=1)