Wrong bundle for group menu menu_link_content

Problem/Motivation

I'm not 100% sure that I got this correctly but it seems to me that we have to use menu_link_content as bundle for group content menu links always. Currently the links migrated with this module end in a Drupal\Component\Plugin\Exception\PluginNotFoundException: The "entity:menu_link_content:group_main" plugin does not exist. error on save.

Steps to reproduce

Run Code like

  $menu_content_migrator = \Drupal::service('sites_migrator.menu_content_migrator');
  $menu_content_migrator->migrateMenuItems('main', 1, 'group_main', 'Main navigation', $output);

To migrate the links and then try to edit and save a migarted link

Proposed resolution

Hard code menu_link_content as bundle.