Allow settings value to be nullified (#8596)

* Allow settings value to be nullified

* Additional null check

* Bump API version

* Fix for unit test

src/backend/InvenTree/InvenTree/api_version.py

@@ -1,13 +1,16 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 290
+INVENTREE_API_VERSION = 291
 
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 
 INVENTREE_API_TEXT = """
 
+v291 - 2024-11-30 : https://github.com/inventree/InvenTree/pull/8596
+    - Allow null / empty values for plugin settings
+
 v290 - 2024-11-29 : https://github.com/inventree/InvenTree/pull/8590
     - Adds "quantity" field to ReturnOrderLineItem model and API
 

src/backend/InvenTree/common/serializers.py

@@ -41,11 +41,19 @@ class SettingsValueField(serializers.Field):
 
         Protected settings are returned as '***'
         """
-        return '***' if instance.protected else str(instance.value)
+        if instance.protected:
+            return '***'
+        elif instance.value is None:
+            return ''
+        else:
+            return str(instance.value)
 
     def to_internal_value(self, data):
         """Return the internal value of the setting."""
-        return str(data)
+        if data is None:
+            return ''
+        else:
+            return str(data)
 
 
 class SettingsSerializer(InvenTreeModelSerializer):
@@ -65,7 +73,13 @@ class SettingsSerializer(InvenTreeModelSerializer):
 
     api_url = serializers.CharField(read_only=True)
 
-    value = SettingsValueField()
+    value = SettingsValueField(allow_null=True)
+
+    def validate_value(self, value):
+        """Validate the value of the setting."""
+        if value is None:
+            return ''
+        return str(value)
 
     units = serializers.CharField(read_only=True)
 
@@ -185,6 +199,12 @@ class GenericReferencedSettingSerializer(SettingsSerializer):
         # resume operations
         super().__init__(*args, **kwargs)
 
+    def validate_value(self, value):
+        """Validate the value of the setting."""
+        if value is None:
+            return ''
+        return str(value)
+
 
 class NotificationMessageSerializer(InvenTreeModelSerializer):
     """Serializer for the InvenTreeUserSetting model."""