feat: implement discount display in various detail drawers

- Added discount amount and percentage display in Bill, Credit Note, Estimate, Invoice, Receipt, and Vendor Credit detail tables.
- Updated models to include discount-related attributes for better data handling.
- Enhanced user interface to show discount information when applicable, improving clarity in financial documents.

packages/server/src/models/Bill.ts

@@ -53,6 +53,10 @@ export default class Bill extends mixin(TenantModel, [
       'localAllocatedCostAmount',
       'billableAmount',
       'amountLocal',
+
+      'discountAmount',
+      'discountPercentage',
+
       'subtotal',
       'subtotalLocal',
       'subtotalExludingTax',