public function findStandardIdentityByIdentifier(string $identifier): Entity\StandardIdentity
    {
        $identity = new Entity\StandardIdentity;
        $identity->setIdentifier($identifier);

        $this->repository->load($identity);

        if ($identity->getId() === null) {
            $this->logger->notice('identity not found', [
                'input' => [
                    'identifier' => $identifier,
                ],
            ]);

            throw new IdentityNotFound;
        }

        return $identity;
    }