E2E Workflow Scripts: Conditionally validate sample applications' authentication with their backends

[imheresamir]

Describe the solution you would like

Currently the E2E workflow validation in bin/test-workflow/9_app_verify_authentication.sh happens through deployment of a cURL pod which pushes and fetches data from the sample application to verify successful password authentication with its backend. This could possibly be done through Helm tests for the specific sample app subcharts of the app-deploy Helm chart.

Describe alternatives you have considered

If a Helm test isn't suitable for this validation, there should at least be environment variables set to select which specific sample app to validate, rather than validating all sample apps unconditionally.

Additional context

Thinking ahead to when we add more application integrations...
Ideally, these curl commands for each app integration should be run conditionally based on env variable.
However, if it's possible to move these calls into Helm tests that are defined for each subchart, then this would be a lot less fugly with conditionals scattered through this test code.

If we're not going to add conditionals (based on env variable enables) for the short term, we should at least file an issue or create a spike to either add conditional logic in, or figure out how to do this as Helm tests in each of the subcharts.

Originally posted by @diverdane in #307 (comment)