Ensure overriding values do not override the one defined by the CR

What it does

1/ Specific keys were forbidden in the clusterSettings field (ex: cluster, k8s_version, etc.) because they are already defined by the CR fields. However, it was possible to do it in the valuesFrom items (like ConfigMaps)

The present MR removes this un-consistency while ensuring that the CR fields have the top priority

• The admission policies are removed
• The generated SylvaUnitsRelease (SUR) spec values are built by the following merging algorithm. It ensures the CRD field priority (CRD fileds > ClusterSetting > OverridingValues)
  1. First, the Overriding values are copied in the final SUR values
  2. Then, the ClusterSetting values are merged
  3. Then, the other CRD fields (ex: k8s_version) are merged

The README is improved to explain this order

2/ The SylvaUnitsRelease generation code is slighlty improved

• Remove some comments without added values. Ex: // Switch case to determine bootstrap_provider based on workloadCluster.Spec.controlPlane.provider just before switch workloadCluster.Spec.ControlPlane.Provider
• Several variables were defined far from where they were used. It has been changed. Ex: infraProvider was defined 25 lines before being used

Tests

A new test is added to ensure that CRD fields are not overridden. See the tests named Creates capd SylvaWorkloadCluster resources and ensures that the merging priorities are correct: key defined in CRD > clusterSettings > overridingValues

• CI Tests ✅
• CI E2E Tests ✅
• Local tests on Openstack ✅

Go vulncheck related to https://pkg.go.dev/vuln/GO-2026-5377, no known fix yet (2026-06-26-16-05)

References

Close #47 (closed)