Books Post Type With Genres and Authors

// Names used in labels and URLs: edit to suit.
$wpide_type = array(
    'name'     => 'book', // Internal name: lowercase, max 20 characters, never change it once you have content.
    'singular' => 'Book',
    'plural'   => 'Books',
    'slug'     => 'books',
);

add_action( 'init', function () use ( $wpide_type ) {
    $s = $wpide_type['singular'];
    $p = $wpide_type['plural'];

    register_post_type( $wpide_type['name'], array(
        'labels'        => array(
            'name'                  => $p,
            'singular_name'         => $s,
            'menu_name'             => $p,
            'add_new_item'          => "Add New $s",
            'edit_item'             => "Edit $s",
            'new_item'              => "New $s",
            'view_item'             => "View $s",
            'view_items'            => "View $p",
            'all_items'             => "All $p",
            'search_items'          => "Search $p",
            'not_found'             => 'Nothing found.',
            'not_found_in_trash'    => 'Nothing found in Trash.',
            'archives'              => "$s Archives",
            'attributes'            => "$s Attributes",
            'insert_into_item'      => "Insert into $s",
            'uploaded_to_this_item' => "Uploaded to this $s",
            'item_published'        => "$s published.",
            'item_updated'          => "$s updated.",
        ),
        'public'        => true,
        'has_archive'   => $wpide_type['slug'],
        'rewrite'       => array( 'slug' => $wpide_type['slug'], 'with_front' => false ),
        'show_in_rest'  => true,
        'menu_icon'     => 'dashicons-book-alt',
        'menu_position' => 30,
        'supports'      => array( 'title', 'editor', 'excerpt', 'thumbnail', 'revisions' ),
    ) );

    register_taxonomy( 'genre', $wpide_type['name'], array(
        'labels'            => array(
            'name'          => 'Genres',
            'singular_name' => 'Genre',
            'menu_name'     => 'Genres',
            'all_items'     => 'All Genres',
            'edit_item'     => 'Edit Genre',
            'view_item'     => 'View Genre',
            'update_item'   => 'Update Genre',
            'add_new_item'  => 'Add New Genre',
            'new_item_name' => 'New Genre Name',
            'search_items'  => 'Search Genres',
            'not_found'     => 'No genres found.',
            'parent_item'   => 'Parent Genre',
        ),
        'hierarchical'      => true,
        'public'            => true,
        'rewrite'           => array( 'slug' => 'genre', 'with_front' => false ),
        'show_admin_column' => true,
        'show_in_rest'      => true,
    ) );

    register_taxonomy( 'book_author', $wpide_type['name'], array(
        'labels'            => array(
            'name'                       => 'Book Authors',
            'singular_name'              => 'Book Author',
            'menu_name'                  => 'Book Authors',
            'all_items'                  => 'All Book Authors',
            'edit_item'                  => 'Edit Book Author',
            'view_item'                  => 'View Book Author',
            'update_item'                => 'Update Book Author',
            'add_new_item'               => 'Add New Book Author',
            'new_item_name'              => 'New Book Author Name',
            'search_items'               => 'Search Book Authors',
            'not_found'                  => 'No book authors found.',
            'popular_items'              => 'Popular Book Authors',
            'separate_items_with_commas' => 'Separate book authors with commas',
            'choose_from_most_used'      => 'Choose from the most used book authors',
        ),
        'hierarchical'      => false,
        'public'            => true,
        'rewrite'           => array( 'slug' => 'book-author', 'with_front' => false ),
        'show_admin_column' => true,
        'show_in_rest'      => true,
    ) );
} );