Implement auto-rounding decimal field

Ref: https://stackoverflow.com/questions/37958130/automatically-round-djangos-decimalfield-according-to-the-max-digits-and-decima

InvenTree/company/forms.py

@@ -6,6 +6,7 @@ Django Forms for interacting with Company app
 from __future__ import unicode_literals
 
 from InvenTree.forms import HelperForm
+from InvenTree.fields import RoundingDecimalFormField
 
 from .models import Company
 from .models import SupplierPart
@@ -64,6 +65,10 @@ class EditSupplierPartForm(HelperForm):
 class EditPriceBreakForm(HelperForm):
     """ Form for creating / editing a supplier price break """
 
+    quantity = RoundingDecimalFormField(max_digits=10, decimal_places=5)
+
+    cost = RoundingDecimalFormField(max_digits=10, decimal_places=5)
+
     class Meta:
         model = SupplierPriceBreak
         fields = [

InvenTree/company/migrations/0011_auto_20200318_1114.py

@@ -0,0 +1,20 @@
+# Generated by Django 2.2.9 on 2020-03-18 11:14
+
+import InvenTree.fields
+import django.core.validators
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('company', '0010_auto_20200201_1231'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='supplierpricebreak',
+            name='cost',
+            field=InvenTree.fields.RoundingDecimalField(decimal_places=5, max_digits=10, validators=[django.core.validators.MinValueValidator(0)]),
+        ),
+    ]

InvenTree/company/migrations/0012_auto_20200318_1114.py

@@ -0,0 +1,20 @@
+# Generated by Django 2.2.9 on 2020-03-18 11:14
+
+import InvenTree.fields
+import django.core.validators
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('company', '0011_auto_20200318_1114'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='supplierpricebreak',
+            name='quantity',
+            field=InvenTree.fields.RoundingDecimalField(decimal_places=5, default=1, max_digits=15, validators=[django.core.validators.MinValueValidator(1)]),
+        ),
+    ]

InvenTree/company/models.py

@@ -21,7 +21,7 @@ from django.conf import settings
 
 from markdownx.models import MarkdownxField
 
-from InvenTree.fields import InvenTreeURLField
+from InvenTree.fields import InvenTreeURLField, RoundingDecimalField
 from InvenTree.status_codes import OrderStatus
 from common.models import Currency
 
@@ -381,9 +381,9 @@ class SupplierPriceBreak(models.Model):
 
     part = models.ForeignKey(SupplierPart, on_delete=models.CASCADE, related_name='pricebreaks')
 
-    quantity = models.DecimalField(max_digits=15, decimal_places=5, default=1, validators=[MinValueValidator(1)])
+    quantity = RoundingDecimalField(max_digits=15, decimal_places=5, default=1, validators=[MinValueValidator(1)])
 
-    cost = models.DecimalField(max_digits=10, decimal_places=5, validators=[MinValueValidator(0)])
+    cost = RoundingDecimalField(max_digits=10, decimal_places=5, validators=[MinValueValidator(0)])
 
     currency = models.ForeignKey(Currency, blank=True, null=True, on_delete=models.SET_NULL)