* define a simple model mixin class for barcode
* Adds generic function for assigning a barcode to a model instance
* StockItem model now implements the BarcodeMixin class
* Implement simple unit tests for new code
* Fix unit tests
* Data migration for uid field
* Remove references to old 'uid' field
* Migration for removing old uid field from StockItem model
* Bump API version
* Change lookup_barcode to be a classmethod
* Change barcode_model_type to be a class method
* Cleanup for generic barcode scan and assign API:
- Raise ValidationError as appropriate
- Improved unit testing
- Groundwork for future generic implementation
* Further unit tests for barcode scanning
* Adjust error messages for compatibility
* Unit test fix
* Fix hash_barcode function
- Add unit tests to ensure it produces the same results as before the refactor
* Add BarcodeMixin to Part model
* Remove old format_barcode function from Part model
* Further fixes for unit tests
* Add support for assigning arbitrary barcode to Part instance
- Simplify barcode API
- Add more unit tests
* More unit test fixes
* Update unit test
* Adds generic endpoint for unassigning barcode data
* Update web dialog for unlinking a barcode
* Template cleanup
* Add Barcode mixin to StockLocation class
* Add some simple unit tests for new model mixin
* Support assigning / unassigning barcodes for StockLocation
* remove failing outdated test
* Update template to integrate new barcode support for StockLocation
* Add BarcodeMixin to SupplierPart model
* Adds QR code view for SupplierPart
* Major simplification of barcode API endpoints
- Separate existing barcode plugin into two separate classes
- Simplify and consolidate the response from barcode scanning
- Update unit testing
* Yet more unit test fixes
* Yet yet more unit test fixes
