Add support for imagePullSecrets

[crburke]

The deployment.yaml file does not support specification of imagePullSecrets.

This is useful for scenarios where this chart is used as a dependency by another chart that includes altering the target image to be used by the deployment.

[N-o-Z]

@crburke Thank you for your contribution. Can you expand a little bit more about your use case?

[crburke]

We have internal tooling to support adding an internal certificate authority to a docker image. To leverage that tooling I needed to build a custom lakeFS image. Once that image was available I wanted to continue using the helm charts provided in this repo, but I needed to be able to provide imagePullSecrets to be able to access the image from our docker registry. To do so I changed lakefs/templates/deployment.yaml to include the following in the spec section, but ideally this would be supported by the chart without any further customization:

{{- if .Values.imagePullSecret }}
imagePullSecrets:
  - name: {{ .Values.imagePullSecret }
{{- end }}

[sverbruggen]

I would also appreciate this function being added to the chart