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/part/models.py

@@ -6,7 +6,7 @@ import decimal
 import hashlib
 import logging
 import os
-from datetime import datetime
+from datetime import datetime, timedelta
 from decimal import Decimal, InvalidOperation
 
 from django.contrib.auth.models import User
@@ -2510,6 +2510,31 @@ class PartPricing(common.models.MetaMixin):
             if purchase_max is None or purchase_cost > purchase_max:
                 purchase_max = purchase_cost
 
+        # Also check if manual stock item pricing is included
+        if InvenTreeSetting.get_setting('PRICING_USE_STOCK_PRICING', True, cache=False):
+
+            items = self.part.stock_items.all()
+
+            # Limit to stock items updated within a certain window
+            days = int(InvenTreeSetting.get_setting('PRICING_STOCK_ITEM_AGE_DAYS', 0, cache=False))
+
+            if days > 0:
+                date_threshold = datetime.now().date() - timedelta(days=days)
+                items = items.filter(updated__gte=date_threshold)
+
+            for item in items:
+                cost = self.convert(item.purchase_price)
+
+                # Skip if the cost could not be converted (for some reason)
+                if cost is None:
+                    continue
+
+                if purchase_min is None or cost < purchase_min:
+                    purchase_min = cost
+
+                if purchase_max is None or cost > purchase_max:
+                    purchase_max = cost
+
         self.purchase_cost_min = purchase_min
         self.purchase_cost_max = purchase_max
 
@@ -2651,6 +2676,7 @@ class PartPricing(common.models.MetaMixin):
                 max_costs.append(self.supplier_price_max)
 
         if InvenTreeSetting.get_setting('PRICING_USE_VARIANT_PRICING', True, cache=False):
+            # Include variant pricing in overall calculations
             min_costs.append(self.variant_cost_min)
             max_costs.append(self.variant_cost_max)