Part pricing cache (#3710)

* Create new model for storing Part pricing data

Currently this model does not "do" anything but will be used for caching pre-calculated pricing information

* Define function for accessing pricing information for a specific part

* Adds admin site support for new PartPricing model

* Specify role for PartPricing model

* Allow blank values for PartPricing model fields

* Add some TODO entries

* Update migration files to sync with latest master

* Expose API endpoint for viewing part pricing information

* Update migration file

* Improvements:

- Updated model with new fields
- Code for calculating BOM price
- Code for calculating internal price
- Code for calculating supplier price
- Updated unit testing

* Fix (and test) for API serializer

* Including min/max pricing data in part serializer

* Bump API version

* Add pricing overview information in part table

- Adds helper function for formatting currency data
- No longer pre-render "price strings" on the server

* Overhaul of BOM API

- Pricing data no longer calculated "on the fly"
- Remove expensive annotation operations
- Display cached price range information in BOM table

* Filter BOM items by "has pricing"

* Part API endpoint can be filtered by price range

* Updpated API version notes

* Improvements for price caching calculations

- Handle null price values
- Handle case where conversion rates are missing
- Allow manual update via API

* Button to manually refresh pricing

* Improve rendering of price-break table

* Update supplier part pricing table

* Updated js functions

* Adds background task to update assembly pricing whenever a part price cache is changed

* Updates for task offloading

* HTML tweaks

* Implement calculation of historical purchase cost

- take supplier part pack size into account
- improve unit tests

* Improvements for pricing tab rendering

* Refactor of pricing page

- Move javascript functions out into separate files
- Change price-break tables to use bar graphs
- Display part pricing history table and chart
- Remove server-side rendering for price history data
- Fix rendering of supplier pricing table
- Adds extra filtering options to the SupplierPriceBreak API endpoint

* Refactor BOM pricing chart / table

- Display as bar chart with min/max pricing
- Display simplified BOM table

* Update page anchors

* Improvements for BOM pricing table display

* Refactoring sales data tables

- Add extra data and filter options to sales order API endpoints
- Display sales order history table and chart

* Add extra fields to PartPricing model:

- sale_price_min
- sale_price_max
- sale_history_min
- sale_history_max

* Calculate and cache sale price data

* Update part pricing when PurchaseOrder is completed

* Update part pricing when sales order is completed

* Signals for updating part pricing cache

- Whenever an internal price break is created / edited / deleted
- Whenever a sale price break is created / edited / deleted

* Also trigger part pricing update when BomItem is created  / edited / deleted

* Update part pricing whenever a supplier price break is updated

* Remove has_complete_bom_pricing method

* Export min/max pricing data in BOM file

* Fix pricing data in BOM export

- Calculate total line cost
- Use more than two digits

* Add pricing information to part export

Also some improvements to part exporting

* Allow download of part category table

* Allow export of stock location data to file

* Improved exporting of StockItem data

* Add cached variant pricing data

- New fields in part pricing model
- Display variant pricing overview in "pricing" tab

* Remove outdated "PART_SHOW_PRICE_HISTORY" setting

* Adds scheduled background task to periodically update part pricing

* Internal prices can optionally override other pricing

* Update js file checks

* Update price breaks to use 6 decimal places

* Fix for InvenTreeMoneySerializer class

- Allow 6 decimal places through the API

* Update for supplier price break table

* javascript linting fix

* Further js fixes

* Unit test updates

* Improve rendering of currency in templates

- Do not artificially limit to 2 decimal places

* Unit test fixes

* Add pricing information to part "details" tab

* Tweak for money formatting

* Enable sort-by-price in BOM table

* More unit test tweaks

* Update BOM exporting

* Fixes for background worker process

- To determine if worker is running, look for *any* successful task, not just heartbeat
- Heartbeat rate increased to 5 minute intervals
- Small adjustments to django_q settings

Ref: https://github.com/inventree/InvenTree/issues/3921
(cherry picked from commit cb26003b92)

* Force background processing of heartbeat task when server is started

- Removes the ~5 minute window in which the server "thinks" that the worker is not actually running

* Adjust strategy for preventing recursion

- Rather than looking for duplicate parts, simply increment a counter
- Add a "scheduled_for_update" flag to prevent multiple updates being scheduled
- Consolidate migration files

* Adds helper function for rendering a range of prices

* Include variant cost in calculations

* Fixes for "has_pricing" API filters

* Ensure part pricing status flags are reset when the server restarts

* Bug fix for BOM API filter

* Include BOM quantity in BOM pricing chart

* Small tweaks to pricing tab

* Prevent caching when looking up settings in background worker

- Caching across mnultiple processes causes issues
- Need to move to something like redis to solve this
- Ref: https://github.com/inventree/InvenTree/issues/3921

* Fixes for /part/pricing/ detail API endpoint

* Update pricing tab

- Consistent naming

* Unit test fixes

* Prevent pricing updates when loading test fixtures

* Fix for Part.pricing

* Updates for "check_missing_pricing"

* Change to pie chart for BOM pricing

* Unit test fix

* Updates

- Sort BOM pie chart correctly
- Simplify PartPricing.is_valid
- Pass "limit" through to check_missing_pricing
- Improved logic for update scheduling

* Add option for changing how many decimals to use when displaying pricing data

* remove old unused setting

* Consolidate settings tabs for pricing and currencies

* Fix CI after changing settings page

* Fix rendering for "Supplier Pricing"

- Take unit pricing / pack size into account

* Extra filtering / ordering options for the SupplierPriceBreak API endpoint

* Fix for purchase price history graph

- Use unit pricing (take pack size into account)

* JS fixes

InvenTree/part/test_api.py

@@ -1182,17 +1182,17 @@ class PartAPITest(InvenTreeAPITestCase):
         url = reverse('api-part-list')
 
         required_cols = [
-            'id',
-            'name',
-            'description',
-            'in_stock',
-            'category_name',
-            'keywords',
-            'is_template',
-            'virtual',
-            'trackable',
-            'active',
-            'notes',
+            'Part ID',
+            'Part Name',
+            'Part Description',
+            'In Stock',
+            'Category Name',
+            'Keywords',
+            'Template',
+            'Virtual',
+            'Trackable',
+            'Active',
+            'Notes',
             'creation_date',
         ]
 
@@ -1217,16 +1217,16 @@ class PartAPITest(InvenTreeAPITestCase):
             )
 
             for row in data:
-                part = Part.objects.get(pk=row['id'])
+                part = Part.objects.get(pk=row['Part ID'])
 
                 if part.IPN:
                     self.assertEqual(part.IPN, row['IPN'])
 
-                self.assertEqual(part.name, row['name'])
-                self.assertEqual(part.description, row['description'])
+                self.assertEqual(part.name, row['Part Name'])
+                self.assertEqual(part.description, row['Part Description'])
 
                 if part.category:
-                    self.assertEqual(part.category.name, row['category_name'])
+                    self.assertEqual(part.category.name, row['Category Name'])
 
 
 class PartDetailTests(InvenTreeAPITestCase):
@@ -1561,6 +1561,56 @@ class PartDetailTests(InvenTreeAPITestCase):
         self.assertIn('Ensure this field has no more than 50000 characters', str(response.data['notes']))
 
 
+class PartPricingDetailTests(InvenTreeAPITestCase):
+    """Tests for the part pricing API endpoint"""
+
+    fixtures = [
+        'category',
+        'part',
+        'location',
+    ]
+
+    roles = [
+        'part.change',
+    ]
+
+    def url(self, pk):
+        """Construct a pricing URL"""
+
+        return reverse('api-part-pricing', kwargs={'pk': pk})
+
+    def test_pricing_detail(self):
+        """Test an empty pricing detail"""
+
+        response = self.get(
+            self.url(1),
+            expected_code=200
+        )
+
+        # Check for expected fields
+        expected_fields = [
+            'currency',
+            'updated',
+            'bom_cost_min',
+            'bom_cost_max',
+            'purchase_cost_min',
+            'purchase_cost_max',
+            'internal_cost_min',
+            'internal_cost_max',
+            'supplier_price_min',
+            'supplier_price_max',
+            'overall_min',
+            'overall_max',
+        ]
+
+        for field in expected_fields:
+            self.assertIn(field, response.data)
+
+        # Empty fields (no pricing by default)
+        for field in expected_fields[2:]:
+            self.assertIsNone(response.data[field])
+
+
 class PartAPIAggregationTest(InvenTreeAPITestCase):
     """Tests to ensure that the various aggregation annotations are working correctly..."""