I am working on a search service. My Spring Boot search service stands between my internal userbase and my Amazon Elastic Search cluster. I want to enable fine-grained access control, however I can't rely on AWS IAM as we have an in-house service to manage Authentication and authorization. Is there any way I can enable fine-grained access control for search without mapping all the users from my system to either IAM, Cognito or Kibana internal database?