Fix login redirect issue

[marcusquinn]

Fix Login Redirect Issue and Enhance Login Form

Description

This PR addresses two related issues:

1. Login Redirect Loop: Users were unable to log in through the frontend login form or access the WordPress admin login page due to a redirection loop between the custom login page and wp-login.php.

2. Login Form Caching Issues: The frontend login form on the /account/ page was not working properly due to caching issues.

Changes Made

Emergency Login Feature

1. Modified maybe_obfuscate_login_url() in inc/checkout/class-checkout-pages.php to add an emergency login parameter check
2. Modified handle_auth_redirect() in inc/sso/class-sso.php to add the same emergency login parameter check
3. Added documentation for the emergency login feature in docs/emergency-login.md

AJAX Login Functionality

1. Created new JavaScript files (login-ajax.js and login-ajax.min.js) to handle AJAX login submissions
2. Updated the Login Form Element class to register and enqueue the AJAX login script
3. Modified the login form template to add a class for JavaScript targeting
4. Added an AJAX handler in the Ajax class to process login requests

Benefits

• Provides a reliable way to access the WordPress login page when needed via the emergency login parameter
• Fixes login issues that could lock administrators out of their sites
• Enhances the frontend login form to use AJAX, bypassing caching issues
• Improves user experience with better error handling and feedback
• Maintains security by still redirecting normal login attempts to the custom login page

Testing

1. Test logging in through the frontend login form on the /account/ page
2. Test accessing wp-admin when logged out
3. Test the emergency login parameter by visiting /wp-login.php?emergency_login=1
4. Verify that the normal login flow still works for regular users
5. Test login with incorrect credentials to verify error handling

Usage

Emergency Login

If a site administrator gets locked out of their site, they can use the emergency login parameter to access the WordPress login page directly:

https://example.com/wp-login.php?emergency_login=1

AJAX Login

The frontend login form now uses AJAX to submit login requests, which:

• Bypasses page caching issues
• Provides immediate feedback on login errors
• Prevents page refreshes on failed login attempts
• Redirects to the appropriate page on successful login