DATABASE_URL does not resolve correctly with custom database type

[netthier]

If I set db.type to postgresql, the chart will template its env secret like this:

DATABASE_URL: $(DB_TYPE)://$(DB_USERNAME):$(DB_PASSWORD)@$(DB_HOSTNAME)/$(DB_DATABASE
)
DB_DATABASE: app
DB_HOSTNAME: partdb-db-rw:5432
DB_PASSWORD: hunter2
DB_TYPE: postgresql

However, Kubernetes requires dependent env variables to be defined explicitly after its dependencies are defined.
DATABASE_URL remains unexpanded even if the DB_ vars are set, preventing the pod from starting successfully.
Adding

extraVars:
  - name: DATABASE_URL
    value: "$(DB_TYPE)://$(DB_USERNAME):$(DB_PASSWORD)@$(DB_HOSTNAME)/$(DB_DATABASE)"

to the values fixes this issue.
I'd assume MAILER_DSN is affected by the same issue.

[netthier]

I also had to add ?serverVersion=17.0 as the pod would otherwise crash with Invalid platform version "" specified.