public function replaceMemberAuthor(User $from, User $to)
    {
        $fromIsMember = false;
        $froms = $this->memberRepo->findByUser($from);
        if (count($froms) > 0) {
            $fromIsMember = true;
        }

        $toIsMember = false;
        $tos = $this->memberRepo->findByUser($to);
        if (count($tos) > 0) {
            $toIsMember = true;
        }

        if ($toIsMember && $fromIsMember) {
            //user kept already have its member entry, delete the old one
            foreach ($froms as $member) {
                $this->objectManager->remove($member);
            }
            $this->objectManager->flush();
        } elseif (!$toIsMember && $fromIsMember) {
            //update entry for kept user
            foreach ($froms as $member) {
                $member->setUser($to);
            }
            $this->objectManager->flush();
        }
    }