Missing a possibility to get a books mlid value for views

Description of the need

To create a books child content, the parent books mlid (menu link ID) is required. With help of this ID it's possible to create a link, which let's make a new book child using the Prepopulate module and the mlid value. The created link has to look like /node/add/book?parent=[!mlid].

Proposed solution

Add a views entry to file: book.views.inc

section:

// menu_links table ...
...
$data['book_menu_links']['mlid'] = array(
    'title' => t('mlid'),
    'help' => t('The mlid of the book page.'),
    'field' => array(
        'handler' => 'views_handler_field_numeric',
        'click sortable' => TRUE,
    ),
        'sort' => array(
            'handler' => 'views_handler_sort',
    ),
);

Alternatives that have been considered

none

Additional information

It's working on manually patched versions.

Draft of feature description for Press Release (1 paragraph at most)

Backdrop now includes providing books menu link IDs to be used on Views.

PR: https://github.com/backdrop/backdrop/pull/4064