Data migration to initially update serial number fields for all stock items

- Also automatically updates serial_int field when saving StockItem

InvenTree/stock/migrations/0069_auto_20211109_2347.py

@@ -0,0 +1,55 @@
+# Generated by Django 3.2.5 on 2021-11-09 23:47
+
+import re
+
+from django.db import migrations
+
+
+def update_serials(apps, schema_editor):
+    """
+    Rebuild the integer serial number field for existing StockItem objects
+    """
+
+    StockItem = apps.get_model('stock', 'stockitem')
+
+    for item in StockItem.objects.all():
+
+        if item.serial is None:
+            # Skip items without existing serial numbers
+            continue
+
+        serial = 0
+
+        result = re.match(r"^(\d+)", item.serial or "")
+
+        if result and len(result.groups()) == 1:
+            try:
+                serial = int(result.groups()[0])
+            except:
+                serial = 0
+
+
+        item.serial_int = serial
+        print(item, item.serial, '->', item.serial_int)
+        item.save()
+
+
+def nupdate_serials(apps, schema_editor):
+    """
+    Provided only for reverse migration compatibility
+    """
+    pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0068_stockitem_serial_int'),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            update_serials,
+            reverse_code=nupdate_serials,
+        )
+    ]