operator: add feature gate for maintenance mode

src/go/k8s/pkg/resources/featuregates/centralized_configuration.go

@@ -19,7 +19,7 @@ const (
 // CentralizedConfiguration feature gate should be removed when the operator
 // will no longer support 21.x or older versions
 func CentralizedConfiguration(version string) bool {
-	if version == "dev" {
+	if version == devVersion {
 		// development version contains this feature
 		return true
 	}

src/go/k8s/pkg/resources/featuregates/common.go

@@ -0,0 +1,14 @@
+// Copyright 2022 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+
+package featuregates
+
+const (
+	devVersion = "dev"
+)

src/go/k8s/pkg/resources/featuregates/maintenance_mode.go

@@ -0,0 +1,32 @@
+// Copyright 2022 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+
+package featuregates
+
+import "github.com/Masterminds/semver/v3"
+
+const (
+	maintenanceModeMajor = uint64(22)
+	maintenanceModeMinor = uint64(1)
+)
+
+// MaintenanceMode feature gate should be removed when the operator
+// will no longer support 21.x or older versions
+func MaintenanceMode(version string) bool {
+	if version == devVersion {
+		// development version contains this feature
+		return true
+	}
+	v, err := semver.NewVersion(version)
+	if err != nil {
+		return false
+	}
+
+	return v.Major() == maintenanceModeMajor && v.Minor() >= maintenanceModeMinor || v.Major() > maintenanceModeMajor
+}