How do we host services that should not expose an external enpoint?

[LucaLanziani]

This is mostly a research task to see if it's possible to have a knative service that doesn't expose a public endpoint.

[zaremba-tomasz]

According to docs this can be done by just labelling knative service as shown below:

1. Current initium deployment
   

2. After adding a label
   

@LucaLanziani adding this feature looks like a low hanging fruit but it seems pretty useful, do we want to implement this?

Potential implementation:

1. Extend initium init config by adding a flag defining whether app/service should be private (public by default).
2. Persisting user choice in .initium config file.
3. Modification of service.yaml.tmpl to add the knative label depending on the user's choice.