Undocumented implementation required for extra data.

[hakanersu]

In ActivityObject interface getExtraData method which i thought enough for including extra data to ActivityStream but it seems ReturnsExtraData implementation required for adding extra data. Is it necessary to implement another interface for extra data?

laravel-activity-streams/src/ValueObjects/ActivityObject.php

Lines 39 to 45 in aea363e

	public static function createFromModel(Model $model, $extraData = []): ActivityObject
	{
	if ($model instanceof ReturnsExtraData) {
	$extraData = $model->getExtraData();
	}
	return new static(get_class($model), $model->getKey(), $extraData);