KAS Deployment has no way of specifying an imagePullSecret

Summary

Currently if we wish to override the image that the kas deployment uses to something in a private repository (e.g. dev.gitlab.org), we are unable to do so, as the deployment object does not allow us to specify an imagePullSecret

Steps to reproduce

Confgiure KAS to use an image on a private registry, requiring authentication to access the image.

Configuration used

(Please provide a sanitized version of the configuration used wrapped in a code block (```yaml))

gitlab:
  kas:
    image:
      pullSecrets:
        - name: my-pull-secret

Current behavior

K8s Failure to fetch the image, as not authorized

Expected behavior

With pullSecrets present, fetch succeeds and Pods start

Versions

• Chart: as of at least a04b998b
• Platform: N/A
• Kubernetes: N/A
• Helm: v3.x

Relevant logs

(Please provide any relevate log snippets you have collected, using code blocks (```) to format)