API Deprecate API that will be renamed

code/SiteConfigLeftAndMain.php

@@ -5,6 +5,7 @@
 use SilverStripe\Admin\LeftAndMain;
 use SilverStripe\CMS\Model\SiteTree;
 use SilverStripe\Control\Director;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\Forms\Form;
 use SilverStripe\Forms\FormAction;
 use SilverStripe\Forms\HiddenField;
@@ -46,6 +47,7 @@ class SiteConfigLeftAndMain extends LeftAndMain
 
     /**
      * @var string
+     * @deprecated 5.4.0 Will be renamed model_class
      */
     private static $tree_class = SiteConfig::class;
 
@@ -147,9 +149,11 @@ public function getEditForm($id = null, $fields = null)
      * @param array $data
      * @param Form $form
      * @return String
+     * @deprecated 5.4.0 Will be replaced with save()
      */
     public function save_siteconfig($data, $form)
     {
+        Deprecation::noticeWithNoReplacment('5.4.0', 'Will be replaced with save()');
         $data = $form->getData();
         $siteConfig = DataObject::get_by_id(SiteConfig::class, $data['ID']);
         $form->saveInto($siteConfig);
@@ -164,7 +168,6 @@ public function save_siteconfig($data, $form)
         return $form->forTemplate();
     }
 
-
     public function Breadcrumbs($unlinked = false)
     {
         return new ArrayList(array(