#! Can be used when the above image_repo is a private registry.
#! Typically the value would be the output of: kubectl create secret docker-registry x --docker-server=https://example.io --docker-username="USERNAME" --docker-password="PASSWORD" --dry-run=client -o json | jq -r '.data[".dockerconfigjson"]'
#! Optional.
image_pull_dockerconfigjson:#! e.g. {"auths":{"https://registry.example.com":{"username":"USERNAME","password":"PASSWORD","auth":"BASE64_ENCODED_USERNAME_COLON_PASSWORD"}}}