feat: Implement return and refund functionality in commerce module

- Added return request handling in return.controller.js
- Implemented webhook handling for PayHere payments in webhook.controller.js
- Created models for coupon redemptions, invoices, orders, order items, payments, payment attempts, payment webhook events, refunds, return items, and return requests.
- Developed services for order management, payment processing, refunds, and returns.
- Introduced validation schemas for payment and return requests.
- Created migration scripts for new database tables related to orders, payments, refunds, and returns.
- Added unit tests for order state transitions and PayHere provider functionality.

app/models/commerce/invoice.model.js

@@ -0,0 +1 @@
+module.exports=(s,D)=>{const M=s.define("Invoice",{id:{type:D.STRING,primaryKey:true},invoice_number:{type:D.STRING(80),allowNull:false,unique:true},order_id:{type:D.STRING,allowNull:false,unique:true},status:{type:D.ENUM("ISSUED","VOID"),allowNull:false},currency:{type:D.STRING(3),allowNull:false},subtotal:{type:D.DECIMAL(15,2),allowNull:false},discount_total:{type:D.DECIMAL(15,2),allowNull:false},shipping_amount:{type:D.DECIMAL(15,2),allowNull:false},tax_amount:{type:D.DECIMAL(15,2),allowNull:false},duty_amount:D.DECIMAL(15,2),grand_total:{type:D.DECIMAL(15,2),allowNull:false},issued_at:{type:D.DATE,allowNull:false},paid_at:D.DATE,document_upload_id:D.INTEGER},{tableName:"invoices",timestamps:true});M.associate=db=>M.belongsTo(db.Order,{foreignKey:"order_id",as:"order"});return M;};