Posit Workbench: Support defining sensitive config values via k8s secrets

[kaypeter87]

This PR is copied over from #535 due to the inactivity of the original author. I have also added the suggested changes from the reviewer.

Applies to

• launcherPem
• secureCookieKey
• userPassword
• database.conf

When doing so, the rstudio-secret is skipped and individual mounts containing the above-mentioned secret values are injected.

This PR is breaking as the items listed are now maps and existing deployments would need to migrate from launcherPem: <value> to launcherPem.value: <value>.

@pat-s tested this in a deployment of theirs and it works as expected so far.

secureCookieKey:
  existingSecret: secure-cookie-key
launcherPem:
  existingSecret: launcher-pem
config:
  database:
    conf:
      existingSecret: database-conf
userPassword:
  existingSecret: workbench-user-password

The advantage of this approach is that it gives power to the users and makes use of "simple" k8s secrets instead of relying on some chart magic which puts together a bundled secret from plain config values.

related #520 #493

[CLAassistant]

All committers have signed the CLA.

[kaypeter87]

Closing as the original author of #535 is currently engaged and active on the original PR.