code: private function createFindBySubjectQueryBuilder()
      {
          $as = $this->getAlias();
          $qb = $this->createQueryBuilder();
  
          return $qb
              ->andWhere($qb->expr()->eq($as . '.subjectIdentity.provider', ':provider'))
              ->andWhere($qb->expr()->eq($as . '.subjectIdentity.identifier', ':identifier'));
      }
docs: Creates a "find by subject" query builder.
  
  @return \Doctrine\ORM\QueryBuilder