ImagePullSecret in every namespace

[bakayolo]

Is your feature request related to a problem? Please describe.

We are taking advantages of cloud node permissions to access the different cloud registry.
Which mean that GKE can access GCR, EKS can access ECR and AKS can access ACR, etc.
But we are not able to use an external registry.

External links:

• https://docs.aws.amazon.com/AmazonECR/latest/userguide/ECR_on_EKS.html
• https://docs.microsoft.com/en-us/azure/aks/cluster-container-registry-integration
• https://cloud.google.com/container-registry/docs/access-control

Describe the solution you'd like

The workflow already use the secret to push images into the registry.
Therefore, it could also duplicate the image into the user namespace and add the imagePullSecrets into the deployment.

Additional context

Might depend on #2.
Please sync up with @bappr before starting this.