Update Helm chart to support TTL index creation

[esune]

#531 introduced a mechanism to set-up an optional TTL index in mongo that purges old records after they "expire". The default behaviour is to not have a TTL set-up, but we will want to have these settings in the Helm chart for ease of deployment.

[loneil]

We presently don't have the TTL index in DEV VCAuth-N (no Helm vals for CONTROLLER_SESSION_TIMEOUT_CONFIG_FILE), but that should pull some default?