Updated Gitlab CI create_secret function for Kubernetes solving the authentication issue to pull the images

gitlab-ci-create_secret-function.sh

  #
  # In order to get Kubernetes to be authorised to fetch the Docker images from
  # the private gitlab registry, we are creating a docker-registry secret.
  #
  function create_gitlab_registry_secret() {
    echo "Creating the gitlab-registry secret ..."
    # Save the JSON to create the gitlab-registry docker-registry secret
    GITLAB_REGISTRY_SECRET_JSON=$(
      kubectl create secret --namespace=$KUBE_NAMESPACE \
                            docker-registry gitlab-registry \
                            --docker-server="$CI_REGISTRY" \
                            --docker-username="${CI_DEPLOY_USER:-$CI_REGISTRY_USER}" \
                            --docker-password="${CI_DEPLOY_PASSWORD:-$CI_REGISTRY_PASSWORD}" \
                            --docker-email="$GITLAB_USER_EMAIL" \
                            --output json \
                            --dry-run
    )

    # Extracts the auths key from the decoded JSON
    AUTHS=$(
      echo $GITLAB_REGISTRY_SECRET_JSON | \
      jq '.data[".dockerconfigjson"]' -r | \
      base64 -d | \
      jq '.auths' -c | \
      base64 | \
      tr -d '\n'
    )

    # Updates the GITLAB_REGISTRY_SECRET_JSON with the removed auths key
    # and replace the Kubernetes secret
    FINAL_JSON=$(
      echo $GITLAB_REGISTRY_SECRET_JSON | \
      sed -e s"/\".dockerconfigjson\":\s\"\([a-zA-Z0-9=]\+\)\"/\".dockerconfigjson\":\"$AUTHS\"/"
    )

    echo $FINAL_JSON | \
    kubectl replace --namespace=$KUBERNETES_NAMESPACE \
                    --force \
                    -f -
  }