feat: salesitem can change/soft delete

shipment/models.py

@@ -302,12 +302,30 @@ class SalesItem(ModelBase):
         default='',
         verbose_name='备注'
     )
+
+    delete_at = models.DateTimeField(
+        null=True,
+        blank=True,
+        verbose_name='删除时间',
+    )
+
+    delete_by = models.ForeignKey(
+        User,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name='deleted_sales_items',
+        verbose_name='删除人',
+    )
     
     class Meta:
         db_table = 'sales_item'
         verbose_name = '销售品'
         verbose_name_plural = '销售品'
         ordering = ['id']
+        permissions = [
+            ('soft_delete_salesitem', 'Can soft delete sales item'),
+        ]
     
     def __str__(self):
         return f'{self.name} x {self.quantity} {self.get_unit_display()}'
@@ -342,6 +360,55 @@ class SalesItem(ModelBase):
             return None
 
 
+class SalesItemChangeRecord(ModelBase):
+    """
+    销售品修改记录。
+
+    记录允许修改字段的变更前后值，以及操作者与操作时间。
+    """
+
+    sales_item = models.ForeignKey(
+        SalesItem,
+        on_delete=models.CASCADE,
+        related_name="change_records",
+        verbose_name="销售品",
+    )
+
+    operator = models.ForeignKey(
+        User,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name="sales_item_change_records",
+        verbose_name="操作者",
+    )
+
+    operated_at = models.DateTimeField(
+        verbose_name="操作时间",
+    )
+
+    before_values = models.JSONField(
+        default=dict,
+        blank=True,
+        verbose_name="修改前的值",
+    )
+
+    after_values = models.JSONField(
+        default=dict,
+        blank=True,
+        verbose_name="修改目标值",
+    )
+
+    class Meta:
+        db_table = "sales_item_change_record"
+        verbose_name = "销售品修改记录"
+        verbose_name_plural = "销售品修改记录"
+        ordering = ["-operated_at", "-id"]
+
+    def __str__(self) -> str:
+        return f"SalesItemChangeRecord #{self.id} - sales_item={self.sales_item_id}"
+
+
 class ShipmentDelivery(ModelBase):
     """
     送货单