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/services/commerce/orderState.service.js

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+const transitions={PENDING_PAYMENT:new Set(["PAID","CANCELLED"]),PAID:new Set(["PROCESSING","REFUND_PENDING"]),PROCESSING:new Set(["READY_FOR_FULFILLMENT","REFUND_PENDING"]),READY_FOR_FULFILLMENT:new Set(["PARTIALLY_FULFILLED","FULFILLED"]),PARTIALLY_FULFILLED:new Set(["FULFILLED"]),FULFILLED:new Set(["COMPLETED"]),COMPLETED:new Set(["REFUND_PENDING"]),REFUND_PENDING:new Set(["PARTIALLY_REFUNDED","REFUNDED"]),PARTIALLY_REFUNDED:new Set(["REFUND_PENDING","REFUNDED"]),CANCELLED:new Set(),REFUNDED:new Set()};const canTransition=(from,to)=>Boolean(transitions[from]?.has(to));const assertTransition=(from,to)=>{if(!canTransition(from,to))throw Object.assign(new Error(`Illegal order transition ${from} -> ${to}`),{code:"ILLEGAL_ORDER_TRANSITION",status:409});};module.exports={transitions,canTransition,assertTransition};