Add test for FFCNR authentication

includes/functions/requests/_setup.php

@@ -579,3 +579,7 @@ function ffcnr_load_child_theme_functions() {
 if ( $action === 'auth' ) {
   require_once __DIR__ . '/_auth.php';
 }
+
+if ( $action === 'test' ) {
+  require_once __DIR__ . '/_test.php';
+}

includes/functions/requests/_test.php

@@ -0,0 +1,19 @@
+<?php
+
+// No direct access!
+defined( 'ABSPATH' ) OR exit;
+
+// Try to get current user
+$user = ffcnr_get_current_user();
+
+// Report
+header( 'Content-Type: text/html; charset=utf-8' );
+header( 'HTTP/1.1 200 OK' );
+
+if ( $user === 0 ) {
+  echo 'FFCNR is not working for unknown, turn it off or try to fix it.';
+} else {
+  echo 'FFCNR is working, all good.';
+}
+
+exit;

includes/functions/settings/_settings_page_general.php

@@ -1164,6 +1164,7 @@
                     )
                   );
                 ?>
+                <p class="inset-paragraph"><a href="<?php echo fictioneer_get_ffcnr_url(); ?>?action=test" target="_blank" rel="noopener"><?php _e( 'Test FFCNR authentication', 'fictioneer' ); ?></a></p>
               </div>
 
               <div class="fictioneer-card__row">