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.

shared/email-components/src/lib/ReceiptPaymentEmail.tsx

@@ -21,10 +21,6 @@ export interface ReceiptEmailTemplateProps {
   // # Colors
   primaryColor?: string;
 
-  // # Invoice total
-  total: string;
-  totalLabel?: string;
-
   // # Receipt #
   receiptNumber?: string;
   receiptNumberLabel?: string;
@@ -32,6 +28,14 @@ export interface ReceiptEmailTemplateProps {
   // # Items
   items: Array<{ label: string; quantity: string; rate: string }>;
 
+  // # Invoice total
+  total: string;
+  totalLabel?: string;
+
+  // # Discount
+  discount?: string;
+  discountLabel?: string;
+
   // # Subtotal
   subtotal?: string;
   subtotalLabel?: string;
@@ -117,7 +121,7 @@ export const ReceiptEmailTemplate: React.FC<
                 <Text style={dueAmountLineItemAmountStyle}>{subtotal}</Text>
               </Column>
             </Row>
-
+            
             <Row style={totalLineRowStyle}>
               <Column width={'50%'}>
                 <Text style={totalLineItemLabelStyle}>{totalLabel}</Text>