add: ca_cert_identifier parameter
rds performance insights
replication_source_identifier default value
Add `replication_source_identifier` var and cluster arn output
Add rds username as a variable with default value
update tf to 0.15.1, add encrypting options, add password generator
Adds support for extra subnets, added in (MR !8)[https://gitlab.lukapo.com/terraform/aws/module.rds/-/merge_requests/8]
feat: upgrade to new version and add some new outputs