feat: Add feature-gates plumbing (#919)

This will be used by upcoming experimental features such as in-cluster
registry. Just adding the plumbing for now.

**What problem does this PR solve?**:

**Which issue(s) this PR fixes**:
Fixes #

**How Has This Been Tested?**:
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Author: jimmidyson

cmd/main.go

@@ -13,6 +13,7 @@ import (
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
 	cliflag "k8s.io/component-base/cli/flag"
+	"k8s.io/component-base/featuregate"
 	"k8s.io/component-base/logs"
 	logsv1 "k8s.io/component-base/logs/api/v1"
 	"k8s.io/component-base/version/verflag"
@@ -32,6 +33,7 @@ import (
 	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/common/pkg/capi/clustertopology/handlers"
 	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/common/pkg/server"
 	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/pkg/controllers/namespacesync"
+	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/pkg/features"
 	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/pkg/handlers/aws"
 	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/pkg/handlers/docker"
 	"github.com/nutanix-cloud-native/cluster-api-runtime-extensions-nutanix/pkg/handlers/generic"
@@ -127,6 +129,12 @@ func main() {
 	namespacesyncOptions.AddFlags(pflag.CommandLine)
 	pflag.CommandLine.SetNormalizeFunc(cliflag.WordSepNormalizeFunc)
 	pflag.CommandLine.AddGoFlagSet(flag.CommandLine)
+
+	// Add feature gate flags.
+	featureGate := featuregate.NewFeatureGate()
+	utilruntime.Must(featureGate.Add(features.DefaultFeatureGates()))
+	featureGate.AddFlag(pflag.CommandLine)
+
 	pflag.Parse()
 
 	verflag.PrintAndExitIfRequested()

pkg/features/feature_gates.go

@@ -0,0 +1,13 @@
+// Copyright 2024 Nutanix. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package features
+
+import "k8s.io/component-base/featuregate"
+
+// DefaultFeatureGates returns all known feature gates.
+// To add a new feature, define a key for it above and add it here. The features will be
+// available throughout the codebase.
+func DefaultFeatureGates() map[featuregate.Feature]featuregate.FeatureSpec {
+	return map[featuregate.Feature]featuregate.FeatureSpec{}
+}