API Set extension hook implementation visibility to protected

code/AdminErrorExtension.php

@@ -16,7 +16,7 @@ class AdminErrorExtension extends Extension
     /**
      * Used by {@see RequestHandler::httpError}
      */
-    public function onBeforeHTTPError($statusCode, HTTPRequest $request, $errorMessage = null)
+    protected function onBeforeHTTPError($statusCode, HTTPRequest $request, $errorMessage = null)
     {
         $controller = $this->getAdminController();
         if (!$controller || Director::is_ajax($request) || $errorMessage === null) {

code/Forms/GridFieldDetailFormPreviewExtension.php

@@ -17,7 +17,7 @@
  */
 class GridFieldDetailFormPreviewExtension extends Extension
 {
-    public function updateItemEditForm(Form $form): void
+    protected function updateItemEditForm(Form $form): void
     {
         $record = $this->owner->getRecord();
         // See LeftAndMain::getEditForm()

code/Forms/GridFieldPrintButtonExtension.php

@@ -11,7 +11,7 @@
  */
 class GridFieldPrintButtonExtension extends Extension
 {
-    public function updatePrintData($data)
+    protected function updatePrintData($data)
     {
         Requirements::css('silverstripe/admin:client/dist/styles/GridField_print.css');
     }

code/Forms/UsedOnTable.php

@@ -83,7 +83,7 @@ public function usage(HTTPRequest $request)
             // Legacy extension hook kept for backwards compatibility
             // Use 'updateUsageExcludedClasses' extension hook instead which prevents database from being queried
             //
-            // Example: public function updateUsage(ArrayList &$usage, DataObject &$record)
+            // Example: protected function updateUsage(ArrayList &$usage, DataObject &$record)
             //     $dataObjects = $usage->exclude('ClassName', MyDataObject::class);
             $this->extend('updateUsage', $usage, $record);
         }

code/LeftAndMainExtension.php

@@ -17,11 +17,11 @@ public function init()
     {
     }
 
-    public function accessedCMS()
+    protected function accessedCMS()
     {
     }
 
-    public function augmentNewSiteTreeItem(&$item)
+    protected function augmentNewSiteTreeItem(&$item)
     {
     }
 }

code/ModelAdmin.php

@@ -381,7 +381,7 @@ public function getExportFields()
      * Archived flag is set to false. That would be best done as an extension, for example:
      *
      * <code>
-     * public function updateList(\SilverStripe\ORM\DataList $list)
+     * protected function updateList(\SilverStripe\ORM\DataList $list)
      * {
      *     return $list->filter('Archived', false);
      * }