Improvements for part creation API endpoint (#4281)

* Refactor javascript for creating a new part

* Simplify method of removing create fields from serializer

* Fix bug which resulted in multiple model instances being created

* remove custom code required on Part model

* Reorganize existing Part API test code

* Add child serializer for part duplication options

* Part duplication is now handled by the DRF serializer

- Improved validation options
- API is self-documenting (no more secret fields)
- More DRY

* Initial stock is now handled by the DRF serializer

* Adds child serializer for adding initial supplier data for a Part instance

* Create initial supplier and manufacturer parts as specified

* Adding unit tests

* Add unit tests for part duplication via API

* Bump API version

* Add javascript for automatically extracting info for nested fields

* Improvements for part creation form rendering

- Move to nested fields (using API metadata)
- Visual improvements
- Improve some field name / description values

* Properly format nested fields for sending to the server

* Handle error case for scrollIntoView

* Display errors for nested fields

* Fix bug for filling part category

* JS linting fixes

* Unit test fixes

* Fixes for unit tests

* Further fixes to unit tests

InvenTree/part/test_part.py

@@ -255,10 +255,6 @@ class PartTest(TestCase):
         self.assertIn('InvenTree', barcode)
         self.assertIn('"part": {"id": 3}', barcode)
 
-    def test_copy(self):
-        """Test that we can 'deep copy' a Part instance"""
-        self.r2.deep_copy(self.r1, image=True, bom=True)
-
     def test_sell_pricing(self):
         """Check that the sell pricebreaks were loaded"""
         self.assertTrue(self.r1.has_price_breaks)