e2e tests

[nabuskey]

We need e2e tests for things we put here. I don't think we have to confine ourselves to Go but all stacks should use the same language and a chosen format.

Tests should:

• Verify functionalities of things that was deployed by stacks. For example, if it deploys Argo Workflows, it should test argo workflows functionalities that are enabled by the stack.
• Verify user workflows. If you instruct users to do things in readme, we should test as much as we can. e.g. Can you login with Keycloak? Can you login to Backstage?

Tests should not:

• Test the core functionalities of things that deploy the stacks. eg. No point in testing idpbuilder's --kind-confgi or --port flags.

Maybe we can mess with https://github.com/microsoft/playwright to start.