Support dual-user config with separate Admin and Base users for DB

[mrandt]

Is your feature request related to a problem? Please describe.

In the official documentation Pega recommends to configure two technical DB users, one for runtime (base user) and one for admin and deployment (admin user). The latter requires elevated privilges.

See following link for reference:
https://docs.pega.com/bundle/platform/page/platform/install/db/k8s-configure-postgres-install.html#database-users-postgres

However, the Pega Helm Charts and container images do not support this dual user config.

values.yaml only has one entry for database username + password:

  jdbc:
    username: "YOUR_JDBC_USERNAME"
    password: "YOUR_JDBC_PASSWORD"

See file: https://github.com/pegasystems/pega-helm-charts/blob/master/charts/pega/values.yaml

Also prconfig.xml is seems to be missing references to JNDI datasources - it only contains those for the single user:

prconfig/database/databases/PegaRULES/dataSourceAdmin
prconfig/database/databases/PegaDATA/dataSourceAdmin

See file: https://github.com/pegasystems/pega-helm-charts/blob/2bd32d6ef773288c292edd7c4465be2c47d1d0cf/charts/pega/config/deploy/prconfig.xml

Last not least, the template files for context.xml also do not contain any extra datasources for Admin DB user:
https://github.com/pegasystems/pega-helm-charts/blob/2bd32d6ef773288c292edd7c4465be2c47d1d0cf/terratest/src/test/pega/data/expectedInstallDeployContext.xml.tmpl

Describe the solution you'd like

If Pega's recommnedation for DB dual user config is still valid, the values.yaml should contain additional properties for usernameAdmin and passwordAdmin - and all other files and mechanisms should be updated accordingly.

If however DB dual user config is no longer encouraged, the documentation should be fixed instead.

Describe alternatives you've considered

Alternative is to stick to a single DB user configuraiton.

Additional context