Feature: Supplier part pack size (#3644)

* Adds 'pack_size' field to SupplierPart model

* Edit pack_size for SupplierPart via API

* Display pack size in supplier part page template

* Improve table ordering for SupplierPart table

* Fix for API filtering

- Need to use custom filter class

* Adds functionality to duplicate an existing SupplierPart

* Bump API version number

* Display annotation of pack size in purchase order line item table

* Display additional information in part purchase order table

* Add UOM to purchase order table

* Improve receive items functionality

* Indicate quantity which will be received in modal form

* Update the received quantity as the user changes the value

* Take  the pack_size into account when receiving line items

* Take supplierpart pack size into account when receiving line items

* Add "pack size" column to purchase order line item table

* Tweak supplier part table

* Update 'on_order' queryset annotation to take pack_size into account

- May god have mercy on my soul

* Adds a unit test to validate that the on_order queryset annotation is working as expected

* Update Part.on_order method to take pack_size into account

- Check in existing unit test also

* Fix existing unit tests

- Previous unit test was actually in error
- Logic for calculating "on_order" was broked

* More unit tests for receiving items against a purchase order

* Allow pack_size < 1

* Display pack size when adding / editing PurchaseOrderLineItem

* Fix bug in part purchase order table

* Update part purchase order table again

* Exclude notificationmessage when exporting dataset

* Also display pack size when ordering parts from secondary form

* javascript linting

* Change user facing strings to "Pack Quantity"

InvenTree/part/models.py

@@ -2036,22 +2036,30 @@ class Part(MetadataMixin, MPTTModel):
 
     @property
     def on_order(self):
-        """Return the total number of items on order for this part."""
-        orders = self.supplier_parts.filter(purchase_order_line_items__order__status__in=PurchaseOrderStatus.OPEN).aggregate(
-            quantity=Sum('purchase_order_line_items__quantity'),
-            received=Sum('purchase_order_line_items__received')
-        )
+        """Return the total number of items on order for this part.
 
-        quantity = orders['quantity']
-        received = orders['received']
+        Note that some supplier parts may have a different pack_size attribute,
+        and this needs to be taken into account!
+        """
 
-        if quantity is None:
-            quantity = 0
+        quantity = 0
 
-        if received is None:
-            received = 0
+        # Iterate through all supplier parts
+        for sp in self.supplier_parts.all():
 
-        return quantity - received
+            # Look at any incomplete line item for open orders
+            lines = sp.purchase_order_line_items.filter(
+                order__status__in=PurchaseOrderStatus.OPEN,
+                quantity__gt=F('received'),
+            )
+
+            for line in lines:
+                remaining = line.quantity - line.received
+
+                if remaining > 0:
+                    quantity += remaining * sp.pack_size
+
+        return quantity
 
     def get_parameters(self):
         """Return all parameters for this part, ordered by name."""