Allow porch namespace in cert/webhook to be configured

[liamfallon]

This PR implements a straightforward fix for Issue 553. It allows the namespace that Porch uses for generation of the deletion validation webhook and certs to be configured by setting the new CERT_NAMESPACE environment variable.

Ideally we should allow the certs and the webhook to be externally specified and then passed to Porch in configuration as suggested in the issue description. However, this PR will allow deployment of Porch in namespaces other than "porch-system" for now.

This PR has been tested manually on a Kind cluster with Porch installed on the default "porch-system" namespace and on a different configured namespace porch-nstest. Below is a fragment of the 3-porch-server.yaml Deployment spec, note the new environment variable CERT_NAMESPACE. Deletion now works in both cases with the appropriate namespace configuration.

       env:
            # Uncomment to enable trace-reporting to jaeger
            #- name: OTEL
            #  value: otel://jaeger-oltp:4317
            - name: OTEL_SERVICE_NAME
              value: porch-server
            - name: CERT_STORAGE_DIR
              value: /etc/webhook/certs
            - name: CERT_NAMESPACE
              value: porch-nstest
          args:
            - --function-runner=function-runner:9445
            - --cache-directory=/cache
            - --cert-dir=/tmp/certs
            - --secure-port=4443

[liamfallon]

/assign @johnbelamaric @tliron @efiacor

[liamfallon]

/retest

[efiacor]

Looks good.
A few minor comments.

[efiacor]

This looks a bit odd also. Hardcoded svc name

[liamfallon]

Yes, That and a number of other things need to be cleaned up. The aim with this PR is to allow the namespace to be changed, whihc is a blocker. I have raised another improvement issue which addresses these other hardcoded values. See nephio-project/nephio#554
The proposal is that rather than having a load of configuration in Porch, we allow users to specify their own webhook where they can specify what they want. The self-signed one here will be retained more for development and integration test. For in-service deployments we will recommend users create and configure their own webhooks.

[kushnaidu]

/approve
Looks good

[efiacor]

/lgtm
/approve

[nephio-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: efiacor, kushnaidu, liamfallon

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