feat: add discount functionality to sales and purchase transactions

- Introduced discount_type and discount fields in Bills and SalesReceipts controllers.
- Updated database migrations to include discount and discount_type in estimates and credit notes tables.
- Enhanced SaleReceipt and SaleEstimate models to support discount attributes.
- Implemented formatting for discount amounts in transformers and PDF templates.
- Updated email templates to display discount information.

This commit enhances the handling of discounts across various transaction types, improving the overall functionality and user experience.

packages/server/src/models/CreditNote.ts

@@ -43,8 +43,18 @@ export default class CreditNote extends mixin(TenantModel, [
       'isPublished',
       'isOpen',
       'isClosed',
+
       'creditsRemaining',
       'creditsUsed',
+
+      'subtotal',
+      'subtotalLocal',
+
+      'discountAmount',
+      'discountPercentage',
+
+      'total',
+      'totalLocal',
     ];
   }