* Pass "Part" instance to plugins when calling validate_serial_number
* Pass part instance through when validating IPN
* Improve custom part name validation
- Pass the Part instance through to the plugins
- Validation is performed at the model instance level
- Updates to sample plugin code
* Pass StockItem through when validating batch code
* Pass Part instance through when calling validate_serial_number
* Bug fix
* Update unit tests
* Unit test fixes
* Fixes for unit tests
* More unit test fixes
* More unit tests
* Furrther unit test fixes
* Simplify custom batch code validation
* Further improvements to unit tests
* Further unit test
- SalesOrderAllocations are no longer created manually
- API endpoint performs data validation
- Multiple line items can be allocated at once
- Adds unit testing for new API endpoint