feat(helm): add basic example helm chart for sample-project-core

[conneryn]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

fixes #(issue)

> helm install my-core-test ./charts/core --namespace sample-project

To test teleport:

> czctl teleport namespace sample-project
> curl http://my-core-test:3000/api

To test intercept:

> czctl intercept service my-core-test -n sample-project
> curl http://my-core-test:3000/api  # still works (unintercepted)
> curl http://my-core-test:3000/api -H "x-c6o-intercept:yes"  # should fail (cause nothing actually running locally)

To demo breaking of intercept after a redeploy:

> helm upgrade my-core-test ./charts/core --namespace sample-project
> curl http://my-core-test:3000/api # DNS could not be resolved?!

It appears the service selector gets munged up so that it doesn't point to any valid pods anymore. Therefore all traffic (even in cluster) fails to resolve my-core-test.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Technical improvement or removal of technical debt.
• Minor change: comments, documentation, trivial fixes

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration.

• Unit Tests

Optional:

• Functional Tests
• Integration Tests