Decouple Elastic Beanstalk RDS from the deployment

AWS has just released some tools for separating RDS from the Elastic Beanstalk deployments: https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2021-10-06-db-decoupling.html

This would be extremely useful for users who have coupled RDS's still with Metabase