fix: handle multiple imagePullSecrets

[toddbaert]

The previous iteration of this was ALMOST working, but:

• it didn't support multiple secrets
• it broke if you did a helm upgrade without a imagePullSecret, forcing the user to use --force.

I've added a sort of hacky "post-processor" script which allows us to add helm control flow where we otherwise couldn't. After talking with @thisthat I think this is the only solution until kustomize supports helm output.

Again, I tested locally, and ImagePullSecrets (even more than one) are added to both the manager deployment and the deployments we create at runtime.

Fixes: #665

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 86.51%. Comparing base (546635e) to head (724fad4).
Report is 13 commits behind head on main.

❗ Current head 724fad4 differs from pull request most recent head b84c1a7

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #666      +/-   ##
==========================================
- Coverage   86.81%   86.51%   -0.30%     
==========================================
  Files          19       19              
  Lines        1577     1587      +10     
==========================================
+ Hits         1369     1373       +4     
- Misses        168      173       +5     
- Partials       40       41       +1     

Files	Coverage Δ
common/flagdproxy/flagdproxy.go	88.70% <100.00%> (+0.53%)	⬆️
controllers/core/flagd/config.go	0.00% <0.00%> (ø)
controllers/core/flagd/resources/deployment.go	94.56% <0.00%> (-5.44%)	⬇️

... and 2 files with indirect coverage changes

Flag	Coverage Δ
unit-tests	86.51% <50.00%> (-0.30%)	⬇️

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[Kavindu-Dodan]

I think this is a good solution to overcome the limitation 👍

[thisthat]

Unfortunately, I believe this is the best solution we could use at the moment until there is a better support for Helm control flow strings in Kustomize :(