Attaching behaviors by section

Module.php

<?php

namespace modules\appmodule;

use Craft;
use craft\elements\Entry;
use craft\events\DefineBehaviorsEvent;
use yii\base\Event;

class Module extends \yii\base\Module
{
    const SECTION_BEHAVIORS = [
        'orders' => [
            \modules\appmodule\behaviors\Order::class,
        ],
    ];

    public function init()
    {
        Event::on(
            Entry::class,
            Entry::EVENT_DEFINE_BEHAVIORS,
            function (DefineBehaviorsEvent $event) {
                $entry = $event->sender;

                // Explicitly checking for sectionId in the body,
                // as it won't be set in $entry yet within the EVENT_BEFORE_SAVE event
                $sectionId = $entry->sectionId || $this->request->getBodyParam('sectionId');
                $section = $sectionId ? Craft::$app->sections->getSectionById($sectionId) : null;

                // Bail early if no section yet
                if (!$section) {
                    return;
                }

                $behaviors = self::SECTION_BEHAVIORS[$section->handle] ?? [];
                $event->behaviors = array_merge($behaviors, $event->behaviors);
            }
        );
    }
}

Order.php

<?php
namespace modules\appmodule\behaviors;

use craft\elements\Entry;
use craft\events\ModelEvent;
use yii\base\Behavior;

class Order extends Behavior
{
    public function events()
    {
        return [
            Entry::EVENT_BEFORE_SAVE => function (ModelEvent $event) {
                // This only works if we check for the sectionId body param
                $event->sender->title = 'Entry::EVENT_BEFORE_SAVE from Behavior::events';
            },
            Entry::EVENT_AFTER_SAVE => function (ModelEvent $event) {
                $entry = $event->sender;
            // This always works
            },
        ];
    }
}