GroupSender::getGroupedByUser

private function getGroupedByUser(array $events): array
{
	$groupedByUser = [];

	foreach ($events as $event)
	{
		$eventType = $event['EVENT'];
		$userIds = $event['USER_IDS'];

		foreach ($userIds as $userId)
		{
			if (!array_key_exists($userId, $groupedByUser))
			{
				$groupedByUser[$userId] = [];
			}
			$groupedByUser[$userId][$eventType] = $eventType;
		}
	}

	return $groupedByUser;
}