fix(connect): propagate sharedStorage.subPath to launcher-managed job volumeMounts

[dbkegley]

Copying this PR so we can run CI and get it merged.
original PR: #774
original author: @hyperbolist

When launcher.enabled, and when sharedStorage.subPath is non-empty, launcher-managed job pod volumeMounts did not prepend that subPath to their job-specific volumeMounts, which had the effect of mounting them higher on the shared storage volume than intended, which caused the job pods to quit immediately when they could not find expected files.

This change ensures that when sharedStorage.subPath is non-empty, it is prepended to the job-specific subPaths of the launcher-managed job pod volumeMounts.

Tested by deploying the chart with clean shared storage volume and fresh database, and then adding a few gallery examples via the web UI, which we could then open and interact with.

fixes #759

Details:

The default values file now prepares an empty value at .Values.launcher.templateValues.sharesStorage.subPath.
https://github.com/FairwindsOps/rstudio-helm/blob/e8ea3daea13f5b1e6ab9ec579d997b1b0a9c2fac/charts/rstudio-connect/values.yaml#L381-L382

The configmap template now pushes .Values.sharedStorage.subPath into the $sessionTemplate for job.tpl to pick up.
https://github.com/FairwindsOps/rstudio-helm/blob/e8ea3daea13f5b1e6ab9ec579d997b1b0a9c2fac/charts/rstudio-connect/templates/configmap.yaml#L60-L63

The job template now looks for the subPath key of .Job.volumeMounts items and prepends $templateData.sharedStorage.subPath to its value if non-empty.
https://github.com/FairwindsOps/rstudio-helm/blob/e8ea3daea13f5b1e6ab9ec579d997b1b0a9c2fac/charts/rstudio-connect/files/job.tpl#L285-L293

[dbkegley]

Ran this locally and confirmed that it works as expected

sharedStorage:
  name: connect-dev-data-pvc
  storageClassName: manual
  create: true
  mount: true
  mountContent: true
  path: /var/lib/rstudio-connect
  subPath: connect-data

launcher:
  enabled: true
  useTemplates: true
  templateValues:
    pod:
      imagePullPolicy: "Always"
    sharedStorage:
      name: connect-dev-data-pvc
      subPath: connect-data

    Mounts:
      /connect/mnt/app from mount0 (rw,path="connect-data/apps/1/1")
      /connect/mnt/job from mount0 (rw,path="connect-data/jobs/1/sLUGS8Fgs1wZhAv3")
      /connect/mnt/python-environments from mount0 (rw,path="connect-data/python-environments")
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-tkjhx (ro)
Conditions:
  Type                        Status
  PodReadyToStartContainers   False
  Initialized                 True
  Ready                       False
  ContainersReady             False
  PodScheduled                True
Volumes:
  mount0:
    Type:       PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:  connect-dev-data-pvc
    ReadOnly:   false

[dbkegley]

That failure was the prepull-daemonset chart so I'm going to ignore it and merge this

 <== Events of namespace posit-test
........................................................................................................................
========================================================================================================================
Deleting release "prepull-daemonset-pdrtq5qxer"...
release "prepull-daemonset-pdrtq5qxer" uninstalled
Error: failed installing charts: failed processing charts

------------------------------------------------------------------------------------------------------------------------
 ✔︎ posit-chronicle => (version: "0.4.6", path: "charts/posit-chronicle")
 ✔︎ rstudio-connect => (version: "0.8.26", path: "charts/rstudio-connect")
 ✔︎ rstudio-launcher-rbac => (version: "0.2.25", path: "charts/rstudio-launcher-rbac")
 ✔︎ rstudio-pm => (version: "0.5.53", path: "charts/rstudio-pm")
 ✔︎ rstudio-workbench => (version: "0.10.6", path: "charts/rstudio-workbench")
 ✖︎ prepull-daemonset => (version: "0.0.5", path: "other-charts/prepull-daemonset") > failed waiting for process: exit status 1