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/paymentWebhookEvent.model.js

@@ -0,0 +1 @@
+module.exports=(s,D)=>s.define("PaymentWebhookEvent",{id:{type:D.STRING,primaryKey:true},provider:{type:D.STRING(30),allowNull:false},provider_event_id:{type:D.STRING(160),allowNull:false},event_type:{type:D.STRING(80),allowNull:false},payload_hash:{type:D.STRING(64),allowNull:false},processing_status:{type:D.ENUM("RECEIVED","PROCESSED","FAILED","IGNORED"),allowNull:false},received_at:{type:D.DATE,allowNull:false},processed_at:D.DATE,error_code:D.STRING},{tableName:"payment_webhook_events",timestamps:true,indexes:[{unique:true,fields:["provider","provider_event_id"]}]});