Improve compatibility with iCloud Keychain

Apple has suggested a scheme for adding TOTP secrets to password managers with a simple click. The solution currently works with Apple’s own password manager iCloud Keychain in Safari on iOS 15, iPad OS 15 and macOS Monterey.
More info: https://developer.apple.com/videos/play/wwdc2021/10105

I wrote a simple proof-of-concept by adding a method called get_totp_link_ref to the WizardSteps class.

**
 * Get TOTP link reference (preview)
 * 
 * Returns a TOTP link reference. For use with the iCloud Keychain and
 * other compatible password managers. 
 *
 * 
 * @return  String
 */

public static function get_totp_link_ref() {
    
    // Get URL encoded site name and domain
    $site_name  = urlencode( get_bloginfo( 'name', 'display' ) );
    $site_url = get_site_url();
    $site_domain = parse_url( $site_url )['host'];
    
    // Get user's username and secrect
    $user_username = wp_get_current_user()->user_login;
    $user_secret = self::getUser()->get_totp_decrypted();
    
    // Create TOTP link target
    $totp_link = 'otpauth://totp/' . '$site_name' . ':' . $user_username . '?secret=' . $user_secret . '&digits=6&time=30&issuer=' . $site_domain;
    
    // Return escaped URL
    return esc_url( $totp_link, array( 'otpauth' ) );
}

The method returns a string that can be as a reference for a dedicated link or a clickable version of the QR code.

<div class="qr-code-wrapper">
    <a href="<?php echo esc_html( self::get_totp_link_ref() ); ?>">
        <?php echo $qrCode; ?>
    </a>
<div>