Fix kubebuilder optional/required markers for API fields

Add missing optional/required markers to resolve kube-api-linter errors
while preserving correct API semantics and discriminated union patterns.

Detailed Change Explanations:

1. api/v1/clustercatalog_types.go

Change: Added // +optional marker to ResolvedCatalogSource.Image field

Reason:
- This is a discriminated union field controlled by the Type field
- XValidation enforces: when Type == "Image", Image is required; otherwise forbidden
- Field is conditionally required, not always required
- Field may be nil during initial reconciliation
- Allows future extensibility
- Fixes kube-api-linter optionalorrequired error

2. api/v1/clusterextension_types.go

Change: Added // +optional marker and omitempty to PreflightConfig.CRDUpgradeSafety

Reason:
- Production code checks for nil
- Field is optional at the Go level
- omitempty follows Kubernetes conventions
- Fixes kube-api-linter optionalorrequired error

3. api/v1/clusterextensionrevision_types.go

Change: Added // +required marker to ClusterExtensionRevisionPhase.Objects

Reason:
- Field is a slice and must always be present
- Tests show empty slice is valid
- No omitempty by design
- Godoc confirms it is required
- Fixes kube-api-linter optionalorrequired error

Author: camilamacedo86

api/v1/clustercatalog_types.go

@@ -246,6 +246,7 @@ type ResolvedCatalogSource struct {
 	Type SourceType `json:"type"`
 	// image contains resolution information for a catalog sourced from an image.
 	// It must be set when type is Image, and forbidden otherwise.
+	// +optional
 	Image *ResolvedImageSource `json:"image"`
 }
 

api/v1/clusterextension_types.go

@@ -405,7 +405,8 @@ type PreflightConfig struct {
 	//
 	// The CRD Upgrade Safety pre-flight check safeguards from unintended consequences of upgrading a CRD,
 	// such as data loss.
-	CRDUpgradeSafety *CRDUpgradeSafetyPreflightConfig `json:"crdUpgradeSafety"`
+	// +optional
+	CRDUpgradeSafety *CRDUpgradeSafetyPreflightConfig `json:"crdUpgradeSafety,omitempty"`
 }
 
 // CRDUpgradeSafetyPreflightConfig is the configuration for CRD upgrade safety preflight check.

api/v1/clusterextensionrevision_types.go

@@ -123,6 +123,7 @@ type ClusterExtensionRevisionPhase struct {
 	// objects is a required list of all Kubernetes objects that belong to this phase.
 	//
 	// All objects in this list are applied to the cluster in no particular order.
+	// +required
 	Objects []ClusterExtensionRevisionObject `json:"objects"`
 }