HMRC API setup

HMRC API Setup
Push_Notification_Configuration
Callback_URL_Setup

I need a developer who understands HMRC APIs and can complete the final setup for my application
The app is already registered with HMRC, and all required APIs have been added. I now need someone to:

• Configure the HMRC push‑notification callback URL
• Generate and correctly store the HMRC push secret
• Set up a working, secure callback endpoint on my server
• Ensure the endpoint returns the correct 2xx response for HMRC validation
• Test the sandbox notifications to confirm everything works
• Explain where the callback URL and push secret are stored in the backend
Goal:
Make sure fully passes HMRC’s API setup requirements so I can start using the sandbox endpoints for self‑employed tax return and VAT submission features.

This is a small but technical task — ideal for someone who has done HMRC integrations before.