Overdue order notification (#3114)

* Adds a background task to notify users when a PurchaseOrder becomes overdue

* Schedule the overdue purchaseorder check to occur daily

* Allow notifications to be sent to "Owner" instances

- Extract user information from the Owner instance

* add unit test to ensure notifications are sent for overdue purchase orders

* Adds notification for overdue sales orders

* Clean up notification display panel

- Simplify rendering
- Order "newest at top"
- Element alignment tweaks

* style fixes

* More style fixes

* Tweak notification padding

* Fix import order

* Adds task to notify user of overdue build orders

* Adds unit tests for build order notifications

* Refactor subject line for emails:

- Use the configured instance title as a prefix for the subject line

* Add email template for overdue build orders

* Fix unit tests to accommodate new default value

* Logic error fix

InvenTree/part/test_part.py

@@ -44,7 +44,7 @@ class TemplateTagTest(InvenTreeTestCase):
 
     def test_inventree_instance_name(self):
         """Test the 'instance name' setting"""
-        self.assertEqual(inventree_extras.inventree_instance_name(), 'InvenTree server')
+        self.assertEqual(inventree_extras.inventree_instance_name(), 'InvenTree')
 
     def test_inventree_base_url(self):
         """Test that the base URL tag returns correctly"""