Finish Stripe + Booking Flow for Existing Yacht Booking App (Next.js + Nestjs)

We are seeking an experienced backend developer to finalize and stabilize an existing yacht/catamaran booking platform for its upcoming launch. The platform is already built with a modern tech stack and requires critical payment integration and system hardening.Current Technology Stack:Frontend: Next.jsBackend: NestJSDatabase: PostgreSQLCompleted Modules:Admin dashboardBooking system with availability managementCustomer and trip managementBasic frontend and booking pagesProject Scope - Key Deliverables:Stripe Payment Integration: Implement comprehensive Stripe integration, including creating payment intents, managing deposit and full payment logic, and setting up webhooks.Payment Confirmation: Develop robust webhook handling to confirm successful payments and update booking statuses accordingly.Booking Integrity: Implement logic to prevent duplicate bookings and validate availability in real-time before payment confirmation.Checkout Flow Development: Connect the existing frontend booking process to the new payment gateway. This includes building a simple, user-friendly checkout page that supports a deposit-first payment model.Error Handling: Design and implement comprehensive error handling for failed payments, including a retry mechanism and ensuring no dead-end states for users.Optional Bonus:WhatsApp Integration: Basic integration using deep links or Twilio for notifications.Required Expertise:Strong proficiency in backend development.Extensive experience with Stripe API, particularly with webhooks.Ability to work effectively with existing codebases and avoid unnecessary refactoring or rebuilding.A commitment to delivering clean, simple, and efficient solutions without over-engineering.Timeline: The project is expected to be completed within 1-2 weeks.Budget: This is a fixed-price project, and we are open to proposals based on your experience and the estimated effort.