Added imagePullSecrets to serviceAccount for images in a private registry

[azun]

Adding the option imagePullSecrets inside the serviceAccount to allow for images in private registries. A list of secret names can be specified in serviceAccount.imagePullSecrets

[spiegela]

@azun Thanks for this. I have also seen this field in other charts labeled registrySecret. Could we rename to this for consistency with ad-hoc Helm standards?

Also, this operator is frequently included as a subchart to others, since ZK is often a component of a larger application. For your use-cases, would it work to nest this value beneath a global block like:

global:
  registrySecret:  <secret-name>

That way this value could be set once in the parent chart?

[azun]

Nesting the secrets under global sounds like a good idea.

I've looked at charts in the official helm/charts github repo and most use a combination of .Values.global.imagePullSecrets and/or .Values.imagePullSecrets/.Values.serviceAccount.imagePullSecrets. I've added global to the chart template, with the option to overwrite it from inside the serviceAccount parameter.

I haven't seen registrySecret used before and imagePullSecrets is more clear in my opinion.

[codecov-commenter]

Codecov Report

Merging #159 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #159   +/-   ##
=======================================
  Coverage   82.41%   82.41%           
=======================================
  Files          11       11           
  Lines        1194     1194           
=======================================
  Hits          984      984           
  Misses        142      142           
  Partials       68       68           

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[SrishT]

LGTM

[anishakj]

Could you please rebase the changes with master, after that we can merge

[azun]

rebased