fix(auth): implement Google OAuth 2.0 login integration in backend and frontend

[Rajal-ui]

Issue Link

Closes #139

Changes Made

Frontend (React / Vite)

• Resolved App Crash: Wrapped the main <App /> component in the <GoogleOAuthProvider> in RestroHub-FrontEnd/src/main.jsx.
• Exposed Client ID: Wired the clientId dynamically via import.meta.env.VITE_GOOGLE_CLIENT_ID.
• Integrated Auth Button: Connected the <GoogleLogin> component inside RestroHub-FrontEnd/src/pages/public/Login.jsx to render the Google Sign-In prompt.
• Documented Env Setup: Added VITE_GOOGLE_CLIENT_ID to RestroHub-FrontEnd/.env.example with instructions on how to obtain credentials.
• Enhanced Documentation: Updated RestroHub-FrontEnd/README.md to reflect proper local installation steps, Vite commands (npm run dev), environment variables, and the correct API path.

Backend (Java / Spring Boot)

• Implemented Verification Service: Developed GoogleAuthService to securely verify Google ID tokens passed from the frontend.
• Created Auth Endpoint: Set up AuthController and the GoogleAuthRequest DTO at /api/v1/auth/google for processing auth flows.
• Database Schema Upgrades: Updated the User entity to map google_sub, auth_provider (e.g., GOOGLE), and profile picture_url columns in PostgreSQL.
• Aligned Environment Properties: Documented all local Spring Boot configurations (DB credentials, JWT keys, and Google Client IDs) within RestroHub/.env.example and application-dev.properties.
• Wrote Unit Tests: Created GoogleAuthServiceTest to comprehensively test authentication, claims verification, and token signature validation.

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Type of Change

• New feature
• Bug fix
• Documentation update
• Code refactor (for discussed optimization)

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Testing Performed

Backend Testing

• Unit tests passed (GoogleAuthServiceTest completes successfully with mock tokens)
• API endpoints tested locally with curl (POST http://localhost:8181/restroly/api/v1/auth/google)
• Database migrations verified (automated Hibernate updates successfully map the new OAuth user columns)
• Test Cases:
  • Test Case 1: Verify that passing a valid Google ID Token returns a secure JWT user session and logs/creates a new user. (Pass)
  • Test Case 2: Verify that passing an expired or invalid Google ID Token returns a 401 Unauthorized response. (Pass)

Frontend Testing

• Component renders correctly (the Login page loads without any blank screens)
• Responsive on mobile/tablet/desktop
• No console errors (the uncaught GoogleOAuthProvider context hook error is fully resolved)
• Test Cases:
  • Test Case 1: Opening the /login route renders the Google Authentication button cleanly. (Pass)
  • Test Case 2: Clicking on the Google Login button launches the official Google account picker popup. (Pass)

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Screenshots/Images

• Before: Opening the login page causes a full-app crash with a blank white screen, throwing: Uncaught Error: Google OAuth components must be used within GoogleOAuthProvider.
• After: The Login page renders beautifully and presents the Google login button correctly:

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Functionality Demo

Steps to Verify Locally

1. Run the Spring Boot backend (./gradlew bootRun inside RestroHub).
2. Run the Vite frontend (npm run dev inside RestroHub-FrontEnd).
3. Open http://localhost:3000/login in your browser.
4. Verify the Google Sign-in button loads and displays the authorization prompt successfully when clicked.

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Additional Notes

• Added highly comprehensive .env.example templates to both projects to make setting up the environment incredibly easy and safe for future contributors.
• Maintained all existing, planned variables (like MongoDB, Redis, and aggregator API definitions) in the backend README.md as per repository guidelines.

[Rajal-ui]

@rdodiya I have fixed the Google OAuth bug now the Log In button works also, fixed the Get Started button correctly links to the dashboard. Sign in button works too without Google OAuth. Could you please review and approve my PR if everything looks good.

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[rdodiya]

Hi @Rajal-ui ,
Please resolve conflicts