Workspaces support

Posted a MR, here are some test steps for this functionality:
1. ddev drush si standard -y
2. ddev drush en -y group_content_menu workspaces
3. Create a new group type (use default settings)
4. Create a new group content menu type. Add a field to it, call it field_test (a plain text field for example).
5. Go to /admin/group/types/manage/default/content and enable the plugin for the created group content menu type (use default settings).
6. Create a new group.
7. Add a new menu to it. Give it a label and populate field_test. Save it.
8. Switch to the stage workspace.
8. Edit the group content menu, update the label and field_test. Verify the form submits successfully and that the fiels are saved.
10. Switch back to the live workspace, try to edit the menu and ensure you see "The content is being edited in the Stage workspace. As a result, your changes cannot be saved.".
11. Publish the changes in the Stage workspace.
12. Go to the Live workspace, edit the group menu and ensure you see the updates values that you entered in the Stage workspace.

Posted an initial review.

Updated!

Posted some comments.

Posted a few comments and replies as well.

I think I addressed all the feedback, but there seems to be something wrong with composer in the test pipeline.

Composer issue is due to https://www.drupal.org/project/gitlab_templates/issues/3463894 📌 Update templates so 11.0 is the default/current branch RTBC .

@amateescu's review was addressed and this works fine here. I think we're good to go.

Automatically closed - issue fixed for 2 weeks with no activity.