Enhance Google Login: Allowed Domains, Redirect URL, Developer Mode, and Logging

[AustinDsza]

Summary

This PR introduces several advanced features to the Login with Google plugin:

• Allowed Email Domains:
  Admins can specify which email domains are permitted to log in via Google.

• Default Redirect URL:
  Admins can set a default URL to redirect users after Google login.

• Developer Mode:
  When enabled, raw Google user data is logged and displayed on the login page for debugging.

• Login Failure Logging:
  All failed login attempts (invalid token, domain restriction, etc.) are logged with a timestamp and reason. Recent logs are viewable in the admin settings.

Implementation Details

• Added new settings fields to the admin page.
• Updated login handler to enforce allowed domains and log failures.
• Added developer mode logic for debug output and logging.
• All new features are configurable via the plugin settings page.

Testing

• Tested on a local XAMPP/WordPress setup.
• Verified all new settings appear and function as expected.
• Confirmed logs and debug output work when developer mode is enabled.

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Please review and let me know if any changes are needed.