Add structured reporting diff to LoggingLogMetric (#6725)

### BRIEF Change description

Fixes #6592

#### WHY do we need this change?

Add structured reporting diff to the controller in
`pkg/controller/direct/logging/logmetric_controller.go`.
The `structuredreporting.ReportDiff` should be used in the `Update`
method of the adapter to report which fields are being updated.
This helps in debugging reconciliation loops and provides better
visibility into what changed.

#### Special notes for your reviewer:

#### Does this PR add something which needs to be 'release noted'?
```release-note
NONE
```

#### Additional documentation e.g., references, usage docs, etc.:
```docs
NONE
```

#### Intended Milestone
- [ ] Reviewer tagged PR with the actual milestone.

### Tests you have done

- [ ] Run `make ready-pr` to ensure this PR is ready for review.
- [ ] Perform necessary E2E testing for changed resources.

Author: cheftako

pkg/controller/direct/logging/logmetric_controller.go

@@ -33,6 +33,7 @@ import (
 	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/controller/direct"
 	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/controller/direct/directbase"
 	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/controller/direct/registry"
+	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/structuredreporting"
 )
 
 const ctrlName = "logmetric-controller"
@@ -249,18 +250,23 @@ func (a *logMetricAdapter) Update(ctx context.Context, updateOp *directbase.Upda
 	latest := a.actual
 
 	if a.hasChanges(ctx, u) {
+		report := &structuredreporting.Diff{Object: updateOp.GetUnstructured()}
+
 		update := new(api.LogMetric)
 		*update = *a.actual
 
 		if direct.ValueOf(a.desired.Spec.Description) != a.actual.Description {
+			report.AddField("description", a.actual.Description, direct.ValueOf(a.desired.Spec.Description))
 			update.Description = direct.ValueOf(a.desired.Spec.Description)
 		}
 		if direct.ValueOf(a.desired.Spec.Disabled) != a.actual.Disabled {
+			report.AddField("disabled", a.actual.Disabled, direct.ValueOf(a.desired.Spec.Disabled))
 			update.Disabled = direct.ValueOf(a.desired.Spec.Disabled)
 		}
 		if a.desired.Spec.Filter != a.actual.Filter {
 			// todo acpana: revisit UX, err out if filter of desired is empty
 			if a.desired.Spec.Filter != "" {
+				report.AddField("filter", a.actual.Filter, a.desired.Spec.Filter)
 				update.Filter = a.desired.Spec.Filter
 			} else {
 				// filter is a REQUIRED field
@@ -270,24 +276,31 @@ func (a *logMetricAdapter) Update(ctx context.Context, updateOp *directbase.Upda
 
 		desired := convertKCCtoAPI(&a.desired.Spec)
 		if !compareMetricDescriptors(desired.MetricDescriptor, a.actual.MetricDescriptor) {
+			report.AddField("metric_descriptor", a.actual.MetricDescriptor, desired.MetricDescriptor)
 			update.MetricDescriptor = desired.MetricDescriptor
 		}
 
 		if !reflect.DeepEqual(a.desired.Spec.LabelExtractors, a.actual.LabelExtractors) {
+			report.AddField("label_extractors", a.actual.LabelExtractors, a.desired.Spec.LabelExtractors)
 			update.LabelExtractors = a.desired.Spec.LabelExtractors
 		}
 
 		if !compareBucketOptions(a.desired.Spec.BucketOptions, a.actual.BucketOptions) {
+			report.AddField("bucket_options", a.actual.BucketOptions, a.desired.Spec.BucketOptions)
 			update.BucketOptions = convertKCCtoAPIForBucketOptions(a.desired.Spec.BucketOptions)
 		}
 
 		if direct.ValueOf(a.desired.Spec.ValueExtractor) != a.actual.ValueExtractor {
+			report.AddField("value_extractor", a.actual.ValueExtractor, direct.ValueOf(a.desired.Spec.ValueExtractor))
 			update.ValueExtractor = direct.ValueOf(a.desired.Spec.ValueExtractor)
 		}
 		if a.desired.Spec.LoggingLogBucketRef != nil && a.desired.Spec.LoggingLogBucketRef.External != a.actual.BucketName {
+			report.AddField("bucket_name", a.actual.BucketName, a.desired.Spec.LoggingLogBucketRef.External)
 			update.BucketName = a.desired.Spec.LoggingLogBucketRef.External
 		}
 
+		structuredreporting.ReportDiff(ctx, report)
+
 		diffs, err := ListFieldDiffs(a.actual, update)
 		if err != nil {
 			// Don't return an error as we're only logging