FInal bank, stripe and paypal sandbox completed

backend/igny8_core/business/billing/models.py

@@ -398,6 +398,20 @@ class Invoice(AccountBaseModel):
     def tax_amount(self):
         return self.tax
 
+    @property
+    def tax_rate(self):
+        """Get tax rate from metadata if stored"""
+        if self.metadata and 'tax_rate' in self.metadata:
+            return self.metadata['tax_rate']
+        return 0
+    
+    @property
+    def discount_amount(self):
+        """Get discount amount from metadata if stored"""
+        if self.metadata and 'discount_amount' in self.metadata:
+            return self.metadata['discount_amount']
+        return 0
+
     @property
     def total_amount(self):
         return self.total