feat: add global.images registry, pullSecrets, and pullPolicy support to k8s-agents-operator

[dpacheconr]

Summary

Add support for cascading registry, pullSecrets, and pullPolicy from global settings to k8s-agents-operator.

Phase 1: Global.Images.Registry Support ✅

• Updated values.yaml with clarifying comments for controller manager image
• Added helper k8s-agents-operator.manager.image in _helpers.tpl to check global.images.registry fallback
• Updated deployment.yaml to use the new image helper

Phase 2: Global.Images.PullSecrets Support ✅

• Added global.images.pullSecrets support to deployment.yaml
• Global and chart-level pullSecrets are concatenated together using concat helper

Phase 3: Global.Images.PullPolicy Support ✅ (NEW)

• Added pullPolicy helper k8s-agents-operator.manager.imagePullPolicy in _helpers.tpl
• Updated deployment.yaml to use pullPolicy helper
• Configuration respects hierarchy: global setting → chart-level setting → default (IfNotPresent)

Configuration Hierarchy

For Image Registry:

1. global.images.registry (if set AND repository matches default)
2. Explicit repository configuration (takes precedence)
3. Default: Docker Hub path

For ImagePullSecrets:

1. global.images.pullSecrets (highest priority)
2. Chart-level controllerManager.manager.image.pullSecrets
   Both sources are concatenated to support flexible secret management.

For ImagePullPolicy:

1. global.images.pullPolicy (highest priority)
2. Chart-level controllerManager.manager.image.pullPolicy
3. Default: IfNotPresent

Implementation Details

• If global.images.registry is set AND repository matches the default, uses global registry
• If repository is explicitly set to custom value, that takes precedence
• If global registry is not set, defaults to Docker Hub path (newrelic/k8s-agents-operator)
• PullPolicy hierarchy ensures global settings cascade down when no explicit chart configuration is provided

Backward Compatibility

✅ Fully backward compatible:

• Existing values.yaml configurations continue to work unchanged
• If controllerManager.manager.image.repository is explicitly set, it takes precedence
• Charts using nri-bundle with global.images.registry now work correctly
• Default behavior unchanged (uses Docker Hub path if neither is set)

Test Plan

Phase 1 (Registry):

• ✓ Global registry is used when set: my.private.registry.com/newrelic/k8s-agents-operator:0.32.2
• ✓ Defaults to Docker Hub when global registry not configured: newrelic/k8s-agents-operator:0.32.2
• ✓ Explicit repository configuration overrides global registry

Phase 2 (PullSecrets):

• ✓ No pullSecrets set → No imagePullSecrets section rendered
• ✓ Global pullSecrets only → Uses global
• ✓ Both global + chart pullSecrets → Uses both (global items first)

Phase 3 (PullPolicy):

• ✓ Global pullPolicy is used when set and no chart-level policy exists
• ✓ Defaults to IfNotPresent when neither global nor chart policy is set
• ✓ Explicit chart-level pullPolicy overrides global setting

Impact

Once merged, users can now configure k8s-agents-operator with global image settings:

```yaml
global:
images:
registry: "my.private.registry.com"
pullSecrets:
- name: my-registry-credentials
pullPolicy: Always
```

This is part of a broader effort to ensure all New Relic Helm charts in the nri-bundle support consistent private registry configuration through global.images settings.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.54%. Comparing base (6a9d2bf) to head (b8c11a6).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #421      +/-   ##
==========================================
- Coverage   69.64%   69.54%   -0.11%     
==========================================
  Files          46       46              
  Lines        2840     2840              
==========================================
- Hits         1978     1975       -3     
- Misses        695      697       +2     
- Partials      167      168       +1     

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