Include stock item purchase price in pricing cache (#4292)

* Add setting to control pricing calculation from stock items

* Bug fix for displaying a "null" setting

* Add new fields to PartPricing model

* Add code for calculation of min/max stock item costs

* Update pricing display to use stock item pricing

* Add unit testing for new pricing features

* Automatically update pricing when stock item is created or edited

* Increment API version

* Improvements for price rendering

* Update based on feedback:

- Roll stock item pricing into purchase pricing
- Simplify models
- Update unit tests

InvenTree/stock/models.py

@@ -1991,6 +1991,10 @@ def after_delete_stock_item(sender, instance: StockItem, **kwargs):
         # Run this check in the background
         InvenTree.tasks.offload_task(part_tasks.notify_low_stock_if_required, instance.part)
 
+        # Schedule an update on parent part pricing
+        if InvenTree.ready.canAppAccessDatabase():
+            instance.part.schedule_pricing_update()
+
 
 @receiver(post_save, sender=StockItem, dispatch_uid='stock_item_post_save_log')
 def after_save_stock_item(sender, instance: StockItem, created, **kwargs):
@@ -2001,6 +2005,9 @@ def after_save_stock_item(sender, instance: StockItem, created, **kwargs):
         # Run this check in the background
         InvenTree.tasks.offload_task(part_tasks.notify_low_stock_if_required, instance.part)
 
+        if InvenTree.ready.canAppAccessDatabase():
+            instance.part.schedule_pricing_update()
+
 
 class StockItemAttachment(InvenTreeAttachment):
     """Model for storing file attachments against a StockItem object."""

InvenTree/stock/templates/stock/item_base.html

@@ -187,7 +187,7 @@
     <tr>
         <td><span class='fas fa-dollar-sign'></span></td>
         <td>{% trans "Purchase Price" %}</td>
-        <td>{{ item.purchase_price }}</td>
+        <td>{% include "price_data.html" with price=item.purchase_price %}</td>
     </tr>
     {% endif %}
     {% if item.parent %}