API Make LinkFieldController a subclass of FormSchemaController

src/Controllers/LinkFieldController.php

@@ -2,7 +2,7 @@
 
 namespace SilverStripe\LinkField\Controllers;
 
-use SilverStripe\Admin\LeftAndMain;
+use SilverStripe\Admin\FormSchemaController;
 use SilverStripe\Control\HTTPResponse;
 use SilverStripe\Forms\DefaultFormFactory;
 use SilverStripe\Forms\Form;
@@ -25,14 +25,12 @@
 use SilverStripe\ORM\Queries\SQLUpdate;
 use SilverStripe\Versioned\Versioned;
 
-class LinkFieldController extends LeftAndMain
+class LinkFieldController extends FormSchemaController
 {
     public const FORM_NAME_TEMPLATE = 'LinkForm_%s';
 
     private static string $url_segment = 'linkfield';
 
-    private static $ignore_menuitem = true;
-
     private static array $url_handlers = [
         'linkForm/$ItemID' => 'linkForm',
         'GET data/$ItemID' => 'linkData',

tests/php/Controllers/LinkFieldControllerTest.php

@@ -251,9 +251,9 @@ public function testLinkFormPost(
         $response = $this->post($url, $data, $headers);
         $this->assertSame($expectedCode, $response->getStatusCode());
         if ($fail === 'csrf-token') {
-            // Will end up at an HTML page with "Silverstripe - Bad Request"
-            $this->assertSame('text/html; charset=utf-8', $response->getHeader('Content-type'));
-            $this->assertStringContainsString('Silverstripe - Bad Request', $response->getBody());
+            // Gives suitable error message for XHR request
+            $this->assertStringStartsWith('text/plain', $response->getHeader('Content-type'));
+            $this->assertStringContainsString('There seems to have been a technical problem', $response->getBody());
             return;
         }
         $this->assertSame($expectedCode, $response->getStatusCode());