feat(#89): add support for pulling the Locust image from private registries

[jachinte]

This pull request implements the feature proposed in #89

I've added some documentation in the getting started page.

Please let me know your thoughts on this PR.

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Note that I could've used Helm's convention to specify images (i.e., an image object with properties repository, tag and pullPolicy, plus an additional property imagePullSecrets) but decided against this because the operator already uses the key image. Doing so would've introduced a breaking change.

[AbdelrhmanHamouda]

Thank you for your kind contribution. It is something that is truly appreciated. I would also like to add additional recognition of writing code that feels native to the implementation already in place.

All and all, amazing work. I have left few comments that I believe are missing to make this PR complete. I would also kindly ask you to include some screenshots / snippets of the generated jobs / pods running with this option. This is so i don't have to setup a private registry myself somewhere and try to test this.

As always nothing is set in stone and everything can be discussed if you have a different opinion.

[AbdelrhmanHamouda]

Hello @jachinte,
I am about to start implementation of a new feature and would like to have your work merged first before I do that.
I understand of course that this is a contribution you provided on your own time but if your time will allow to give this more attention soon, I will wait. Otherwise I will move forward and if needed this PR when the time comes can be reconciled.

[jachinte]

Hi @AbdelrhmanHamouda,
First of all, thank you for the detailed review and nice suggestions. I really appreciate it and feel welcomed to contribute.

I've applied the changes you suggested. I also added the the missing option Never to the imagePullPolicy option. I don't see a reason not to do it.

Here are some screenshots using a private image from the Github Container Registry, on a local k3s cluster:

Create a local cluster using k3d

Create the target namespace and a configmap based on the test module

Install the operator in the target namespace

Note that I packaged the operator locally and published a custom image to Docker Hub

Create a secret in the target namespace for using the Github Container Registry

The custom resource

Deploy the custom resource and monitor created jobs, pods and locust tests

Inspect the latest events to confirm everything worked as expected

[AbdelrhmanHamouda]

thank you for the nice contribution. The failing test seems to be coming from a change in the github action that is not related to this PR. I will have to work on it independently

[AbdelrhmanHamouda]

@jachinte As expected that merging the other PRs caused a conflict on this one. I would resolve it myself but I see that you didn't allow changes by the reviewer. To be this PR is ready to merge, simply solve the conflict and I will merge directly.

[codecov]

Codecov Report

Merging #98 (81b5468) into master (dabc29a) will not change coverage.
The diff coverage is 87.50%.

@@            Coverage Diff            @@
##             master      #98   +/-   ##
=========================================
  Coverage     94.70%   94.70%           
  Complexity       79       79           
=========================================
  Files            12       12           
  Lines           378      378           
  Branches         11       11           
=========================================
  Hits            358      358           
  Misses           16       16           
  Partials          4        4           

Impacted Files	Coverage Δ
...cust/operator/controller/utils/LoadGenHelpers.java	96.59% <80.00%> (ø)
...utils/resource/manage/ResourceCreationHelpers.java	99.40% <90.90%> (ø)

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[jachinte]

@AbdelrhmanHamouda I've resolved the merge conflicts.