Feature Request: Add i18n and l10n Support to FastAPI Backend for Localized Responses

Objective:

Enable the FastAPI backend to support localized responses and internationalized messaging based on the user's language preference.

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Tasks & Requirements:

1. Library Integration

   • Use a FastAPI-compatible i18n tool (options include):

     • fastapi-babel
     • python-babel with gettext
     • Custom middleware to handle Accept-Language headers

2. Language Detection

   • Detect language preference via:

     • Accept-Language HTTP header
     • Optional query parameter (e.g., ?lang=hi)
     • Default to English (en) if none provided

3. Localized API Responses

   • Localize error messages, validation messages, and success responses
   • Use translation keys or message catalogs (e.g., .po/.mo or .json)

4. Session/User Context Support

   • Optionally store user's preferred language in session or user profile
   • Future-proof for per-user language settings

5. Fallback Handling

   • Ensure fallback to English if translation is missing or invalid

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Deliverables:

• Middleware for detecting and applying language preferences
• Localized messages returned from APIs
• Initial translations for at least 2 languages
• Simple example endpoint (e.g., /greet) demonstrating localization in action

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Priority: Medium to High

Improves inclusivity and consistency in backend messaging, especially for API consumers and end users receiving error or validation messages.