Add and document REST APIs using Swagger/OpenAPI

[kmuwanga83]

📌 Problem

There is no clear API documentation for developers integrating with the system.

🎯 Objective

Provide interactive API documentation using Swagger/OpenAPI.

✅ Tasks

• Integrate Swagger/OpenAPI (SpringDoc if using Spring Boot)
• Annotate controllers and endpoints
• Provide sample requests and responses
• Document base URL and endpoints in README

🧪 Acceptance Criteria

• Swagger UI is accessible via browser
• All endpoints are documented
• Developers can test APIs interactively

[gouranga25]

Hi! I've reviewed the API routes and the contributing guidelines, and I'd be happy to work on this API documentation.