[Plugin] Allow custom plugins for running validation routines (#3776)

* Adds new plugin mixin for performing custom validation steps

* Adds simple test plugin for custom validation

* Run part name and IPN validators checks through loaded plugins

* Expose more validation functions to plugins:

- SalesOrder reference
- PurchaseOrder reference
- BuildOrder reference

* Remove custom validation of reference fields

- For now, this is too complex to consider given the current incrementing-reference implementation
- Might revisit this at a later stage.

* Custom validation of serial numbers:

- Replace "checkIfSerialNumberExists" method with "validate_serial_number"
- Pass serial number through to custom plugins
- General code / docstring improvements

* Update unit tests

* Update InvenTree/stock/tests.py

Co-authored-by: Matthias Mair <code@mjmair.com>

* Adds global setting to specify whether serial numbers must be unique globally

- Default is false to preserve behaviour

* Improved error message when attempting to create stock item with invalid serial numbers

* Add more detail to existing serial error message

* Add unit testing for serial number uniqueness

* Allow plugins to convert a serial number to an integer (for optimized sorting)

* Add placeholder plugin methods for incrementing and decrementing serial numbers

* Typo fix

* Add improved method for determining the "latest" serial number

* Remove calls to getLatestSerialNumber

* Update validate_serial_number method

- Add option to disable checking for duplicates
- Don't pass optional StockItem through to plugins

* Refactor serial number extraction methods

- Expose the "incrementing" portion to external plugins

* Bug fixes

* Update unit tests

* Fix for get_latest_serial_number

* Ensure custom serial integer values are clipped

* Adds a plugin for validating and generating hexadecimal serial numbers

* Update unit tests

* Add stub methods for batch code functionality

* remove "hex serials" plugin

- Was simply breaking unit tests

* Allow custom plugins to generate and validate batch codes

- Perform batch code validation when StockItem is saved
- Improve display of error message in modal forms

* Fix unit tests for stock app

* Log message if plugin has a duplicate slug

* Unit test fix

Co-authored-by: Matthias Mair <code@mjmair.com>

InvenTree/part/api.py

@@ -25,8 +25,8 @@ from company.models import Company, ManufacturerPart, SupplierPart
 from InvenTree.api import (APIDownloadMixin, AttachmentMixin,
                            ListCreateDestroyAPIView)
 from InvenTree.filters import InvenTreeOrderingFilter
-from InvenTree.helpers import (DownloadFile, increment, isNull, str2bool,
-                               str2int)
+from InvenTree.helpers import (DownloadFile, increment_serial_number, isNull,
+                               str2bool, str2int)
 from InvenTree.mixins import (CreateAPI, ListAPI, ListCreateAPI, RetrieveAPI,
                               RetrieveUpdateAPI, RetrieveUpdateDestroyAPI,
                               UpdateAPI)
@@ -717,16 +717,16 @@ class PartSerialNumberDetail(RetrieveAPI):
         part = self.get_object()
 
         # Calculate the "latest" serial number
-        latest = part.getLatestSerialNumber()
+        latest = part.get_latest_serial_number()
 
         data = {
             'latest': latest,
         }
 
         if latest is not None:
-            next_serial = increment(latest)
+            next_serial = increment_serial_number(latest)
 
-            if next_serial != increment:
+            if next_serial != latest:
                 data['next'] = next_serial
 
         return Response(data)