Easier DB CA certificate configuration

[Tymek]

Describe the feature request

I'd like to have an ability to configure path to CA certificate instead of having to put file contents as an environment variable. Currently it's only possible by creating my own Docker image.

Background

When using AWS Helm chart it's hard to interpolate variables, like reading file contents with cat. Shell is not available. Also, CA files can be longer then allowed secret length.

Solution suggestions

In addition to DATABASE_SSL if we add an environment variable like DATABASE_CA we can point it to a file mounted in RDS.

volumeMounts:
        - name: rds-pem
          mountPath: /certificates
env:
          DATABASE_HOST: dfdsfdsfdfdfdf.rds.amazonaws.com
          DATABASE_NAME: unleash
          DATABASE_CA: /certificates/regional-bundle.pem

Other informations

Request source: https://unleash-community.slack.com/archives/C03GWTN7XMG/p1711446883483999
Internal ticket: https://linear.app/unleash/issue/SR-509/easier-db-ca-certificate-configuration

[chriswk]

So I started the work in #6892 - My thought is that you can either build one json file with the four needed keys or tell us where your CA, CERT and KEY files with separate env variables.