make the serving port for idpBuilder configurable

[nimakaviani]

• add a --port flag to configure the default port
• add go templates directives to override embedded resource manifests
• template kind cluster config
• add a sample script to tweak the port for the reference example

closes #139

[nimakaviani]

This PR only dynamically changes the port for the embedded tools and configurations. For external configurations (e.g. the reference implementation) it is left up to the users to make the required modifications to change the port.

For the reference example implementation, the PR also includes a small script that can help users tweak the port prior to deploying the reference implementation. This should help in places such as codespaces where there is a desire to use a port different from the default 8443 port.

[nabuskey]

LGTM

[cmoulliard]

I know that most of the URLs that we are proposing should be exposed using HTTPS/TLS (= 8443 or 443) BUT ideally we should also allow to configure the port 80 like this

Source: https://github.com/snowdrop/k8s-infra/blob/main/kind/kind.sh#L505-L512
  - containerPort: ${INGRESS_80_CONTAINER_PORT}
    hostPort: ${INGRESS_80_CONTAINER_PORT}
    protocol: TCP
    listenAddress: "0.0.0.0"
  - containerPort: ${INGRESS_443_CONTAINER_PORT}
    hostPort: ${INGRESS_443_CONTAINER_PORT}
    protocol: TCP
    listenAddress: "0.0.0.0"

@nimakaviani

[nimakaviani]

any particularly usecase @cmoulliard where we cant get away with 443 and require 80 to be open as well? would really like to avoid it unless we really need to.

[cmoulliard]

any particularly usecase @cmoulliard where we cant get away with 443 and require 80 to be open as well?

No. We need both ports and to be able to setup: 80 and 443, etc as ingress's proxy handle HTTP or HTTPS traffic ;-)