Neither global.sql.datasource.username.secretRef/Key nor *SetupJob.username.secretRef/Key work

[megri]

Describe the bug
Using chart version 0.4.39 which is latest version at the time of writing.

When setting any *.username.secretRef/secretKey the chart won't build properly and errors out with

Error: could not merge values: wrong node kind: expected ScalarNode but got MappingNode: node contents:
secretKey: bar
secretRef: foo

To Reproduce
Using this kustomization.yaml:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
helmCharts:
  - name: datahub-prerequisites
    releaseName: datahub-prerequsites
    repo: https://helm.datahubproject.io/
    version: 0.1.13
  - name: datahub
    releaseName: datahub
    repo: https://helm.datahubproject.io/
    version: 0.4.39
    valuesInline:
      global:
        sql:
          datasource:
            username:
              secretRef: foo
              secretKey: bar

the error can be observed.

Expected behavior
Templates seem to indicate that it should be possible to set the username by secret, like here:

• https://github.com/acryldata/datahub-helm/blob/datahub-0.4.39/charts/datahub/subcharts/datahub-gms/templates/deployment.yaml#L152-L159

These PR also indicate that this should be supported:

• feat: allow pulling ebean username from secrets alongside password #291
• feat(sql): allow providing username from secret for sql setup jobs #380