[BE] API Versioning Strategy: Header-based v1/v2 Routing

[emdevelopa]

Description

To avoid breaking changes for merchants, we need a robust API versioning strategy. Instead of URL versioning (e.g. /v1/), we will implement Header-based versioning (Accept-Version: 1).

Requirements and context

• Create a middleware in backend/src/app.js that detects the version header.
• Structure routes into src/routes/v1 and src/routes/v2 respectively.
• Default to v1 if no header is provided.

Suggested execution

• Fork the repo and create a branch: git checkout -b feature/api-versioning
• Implement changes:
  • Refactor createApp to mount version-specific routers.
  • Implement a fallback mechanism for shared logic.
• Test and commit:
  • Use curl -H "Accept-Version: 1" to verify routing.

Example commit message

arch: implement header-based API versioning

Guidelines

• Complexity: High (200 points)