public function generateStringTo(array $receivers, array $groups, array $workspaces)
    {
        $usernames = [];

        foreach ($receivers as $receiver) {
            $usernames[] = $receiver->getUsername();
        }

        $string = implode(';', $usernames);

        foreach ($groups as $group) {
            $el = '{'.$group->getName().'}';
            $string .= '' === $string ? $el : ';'.$el;
        }

        foreach ($workspaces as $workspace) {
            $el = '['.$workspace->getCode().']';
            $string .= '' === $string ? $el : ';'.$el;
        }

        return $string;
    }