UserForm: Fix redirect when renaming a user

refs #8826

application/forms/Config/UserForm.php

@@ -67,6 +67,24 @@ class UserForm extends RepositoryForm
         $this->setSubmitLabel($this->translate('Save'));
     }
 
+    /**
+     * Update a user
+     *
+     * @return  bool
+     */
+    protected function onUpdateSuccess()
+    {
+        if (parent::onUpdateSuccess()) {
+            if (($newName = $this->getValue('user_name')) !== $this->getIdentifier()) {
+                $this->getRedirectUrl()->setParam('user', $newName);
+            }
+
+            return true;
+        }
+
+        return false;
+    }
+
     /**
      * Retrieve all form element values
      *