feat(auth): implement Google OAuth 2.0 authentication

[devstygian]

Summary

Implement Google OAuth 2.0 authentication to provide a secure and convenient login method for administrators and staff members.

The existing email and password authentication should remain available as an alternative login option.

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Objectives

• Integrate Google Sign-In.
• Authenticate users using Google OAuth 2.0.
• Automatically create user accounts during first-time login.
• Link existing accounts based on email address.
• Maintain secure user sessions.

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Functional Requirements

• Add a "Continue with Google" button to the login page.
• Authenticate users through Google OAuth.
• Retrieve user profile information.
• Automatically create accounts for new users.
• Link existing accounts using email matching.
• Store authentication provider information.
• Maintain user sessions after authentication.
• Support secure logout.

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User Information

Store the following information:

• Google ID
• Full Name
• Email Address
• Profile Picture (optional)
• Authentication Provider
• Last Login Timestamp

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Database Changes

users

Add the following fields:

• google_id
• avatar
• auth_provider
• last_login

Example values for auth_provider:

• local
• google

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Security Requirements

• Validate Google ID Tokens.
• Prevent duplicate user accounts.
• Use secure session management.
• Restrict authentication to verified Google accounts.
• Protect OAuth credentials using environment variables.

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Acceptance Criteria

• Users can authenticate using Google Sign-In.
• Existing email/password authentication remains functional.
• Duplicate accounts are prevented.
• User information is stored correctly.
• Sessions remain active after successful authentication.
• Logout terminates the authenticated session securely.

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References

Google Identity Services

https://developers.google.com/identity

Google API Client for PHP

https://github.com/googleapis/google-api-php-client

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Priority

Medium

Labels

enhancement
authentication
oauth
security
google
backend