API based port forwarding

[csweichel]

Is your feature request related to a problem? Please describe.
When I don't have access to the Werft Kubernetes cluster, I still want to use port forwarding to debug the job.

Describe the solution you'd like
Have an API based port forwarding I can consume using the CLI.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.