Add Metadata to further models (#4410)

* Add metadata for ManufacturerPart

* Add Metadata for SupplierPart

* Add metadata to label models

* Add metadata to order line items

* Add metadata to shipment

* Add metadata to Build and BuildItem

* Add metadata to BomItem

* Add metadata to PartParameterTemplate

* Syntax, lint

* Fix isort style

* Lint

* Correction of model name

* Metadata for Reports

* Fix silly error

* Fix silly error

* Correct model name

* Correct model name

* Correction

* Correct company urls

* Apply generic model to Report metadat

* Rename/remove redundant import

* Remove shadowing of report in loop variable

* Update import ordering

* More corrections

* better docstrings

* Correct names for API endpoints

* Default to PO, required for api-doc to work

* Changes by @matmair

* Suppress metadata from Bom export

* Add migration files

* Increment API version

* Add tests for all Metadata models, even previously existing ones

* Update tests

* Fix

* Delay tests

* Fix imports

* Fix tests

* API Version number

* Remove unused import

* isort

* Revent  unintended change of cache

InvenTree/order/test_sales_order.py

@@ -11,7 +11,8 @@ import order.tasks
 from common.models import InvenTreeSetting, NotificationMessage
 from company.models import Company
 from InvenTree import status_codes as status
-from order.models import (SalesOrder, SalesOrderAllocation, SalesOrderLineItem,
+from order.models import (SalesOrder, SalesOrderAllocation,
+                          SalesOrderExtraLine, SalesOrderLineItem,
                           SalesOrderShipment)
 from part.models import Part
 from stock.models import StockItem
@@ -54,6 +55,9 @@ class SalesOrderTest(TestCase):
         # Create a line item
         cls.line = SalesOrderLineItem.objects.create(quantity=50, order=cls.order, part=cls.part)
 
+        # Create an extra line
+        cls.extraline = SalesOrderExtraLine.objects.create(quantity=1, order=cls.order, reference="Extra line")
+
     def test_so_reference(self):
         """Unit tests for sales order generation"""
 
@@ -293,3 +297,22 @@ class SalesOrderTest(TestCase):
 
         # However *no* notification should have been generated for the creating user
         self.assertFalse(messages.filter(user__pk=3).exists())
+
+    def test_metadata(self):
+        """Unit tests for the metadata field."""
+        for model in [SalesOrder, SalesOrderLineItem, SalesOrderExtraLine, SalesOrderShipment]:
+            p = model.objects.first()
+
+            self.assertIsNone(p.metadata)
+
+            self.assertIsNone(p.get_metadata('test'))
+            self.assertEqual(p.get_metadata('test', backup_value=123), 123)
+
+            # Test update via the set_metadata() method
+            p.set_metadata('test', 3)
+            self.assertEqual(p.get_metadata('test'), 3)
+
+            for k in ['apple', 'banana', 'carrot', 'carrot', 'banana']:
+                p.set_metadata(k, k)
+
+            self.assertEqual(len(p.metadata.keys()), 4)