change permissions name unique

apps/product/models.py

@@ -92,3 +92,18 @@ class AttributeValue(BaseModel):
 
     def save(self, *args, **kwargs):
         return super(AttributeValue, self).save(*args, **kwargs)
+
+
+class SaleUnit(BaseModel):
+    product = models.ForeignKey(
+        ReferenceProduct,
+        on_delete=models.CASCADE,
+        related_name='sale_unit',
+        null=True
+    )
+    unit = models.CharField(max_length=255, null=True)
+    variation_coefficient = models.CharField(max_length=255, null=True)
+    required = models.BooleanField(default=False)
+
+    def __str__(self):
+        return f'{self.product} - {self.unit} - {self.variation_coefficient}'