feat: balance api

business/models.py

@@ -420,3 +420,45 @@ class ReceiptOrder(OrderDirectionMixin, OrderCounterpartyMixin, ModelBase):
 
     def get_counterparty_field_name(self) -> str:
         return 'customer'
+
+
+class SupplierBalance(ModelBase):
+    merchant = models.ForeignKey(
+        basic_info_models.Merchant,
+        on_delete=models.PROTECT,
+        related_name='supplier_balances',
+        verbose_name='所属商户',
+    )
+    supplier = models.ForeignKey(
+        basic_info_models.Supplier,
+        on_delete=models.PROTECT,
+        related_name='balances',
+        verbose_name='供应商',
+    )
+    balance = models.DecimalField(max_digits=15, decimal_places=2, default=Decimal('0'), verbose_name='应付余额')
+
+    class Meta:
+        verbose_name = '供应商余额'
+        verbose_name_plural = '供应商余额'
+        unique_together = ('merchant', 'supplier')
+
+
+class CustomerBalance(ModelBase):
+    merchant = models.ForeignKey(
+        basic_info_models.Merchant,
+        on_delete=models.PROTECT,
+        related_name='customer_balances',
+        verbose_name='所属商户',
+    )
+    customer = models.ForeignKey(
+        basic_info_models.Customer,
+        on_delete=models.PROTECT,
+        related_name='balances',
+        verbose_name='客户',
+    )
+    balance = models.DecimalField(max_digits=15, decimal_places=2, default=Decimal('0'), verbose_name='应收余额')
+
+    class Meta:
+        verbose_name = '客户余额'
+        verbose_name_plural = '客户余额'
+        unique_together = ('merchant', 'customer')