working with private image registry

[Shashankft9]

there are two issues to solve when working with private image registry:

• ability to access the registry through some hostalias set in task pods if using on-cluster-build
• ability to mark the ca of the registry as trusted for both local and on-cluster-builds

This is a requirement that we are trying to solve in our env where both image registry and git repository are private - there is another issue for private git repo here: #849

[Shashankft9]

I have tried to solve this in on-cluster build in following way:

for accessibility, I have configured coredns, but I'd much prefer if there is an easy way for the task pods to use hostalias.
for ca

• updated the buildpacks task's "create" step (env and volumeMounts) and volumes sections like this:

      env:
        - name: DOCKER_CONFIG
          value: $(workspaces.dockerconfig.path)
        - name: SSL_CERT_FILE
          value: /etc/registry-ce

      volumeMounts:
        - name: layers-dir
          mountPath: /layers
        - name: $(params.PLATFORM_DIR)
          mountPath: /platform
        - mountPath: /etc/registry-cert
          name: registry-cert

  volumes:
    - name: empty-dir
      emptyDir: {}
    - name: layers-dir
      emptyDir: {}
    - configmap:
        name: registry-cert
      name: registry-cert  

• created a ca cert configmap in the namespace where the tasks and pipelines are going to run:

apiVersion: v1
data:
  ca.crt: |+
    -----BEGIN CERTIFICATE-----
    xxx
    -----END CERTIFICATE-----

kind: ConfigMap
metadata:
  name: registry-cert