core: add comment warning to keep k8sutil hashing consistent

The name generation utils need to provide consistent outputs across
versions so that names generated based on values are consistent and
older generated keys are not lost.

Signed-off-by: Rohan CJ <rohantmp@gmail.com>

pkg/operator/k8sutil/k8sutil.go

@@ -80,6 +80,8 @@ func GetK8SVersion(clientset kubernetes.Interface) (*version.Version, error) {
 }
 
 // Hash stableName computes a stable pseudorandom string suitable for inclusion in a Kubernetes object name from the given seed string.
+// Do **NOT** edit this function in a way that would change its output as it needs to
+// provide consistent mappings from string to hash accross versions of rook.
 func Hash(s string) string {
 	h := sha256.Sum256([]byte(s))
 	return hex.EncodeToString(h[:16])
@@ -91,6 +93,8 @@ func Hash(s string) string {
 // For more information, see the following resources:
 // https://stackoverflow.com/a/50451893
 // https://stackoverflow.com/a/32294443
+// Do **NOT** edit this function in a way that would change its output as it needs to
+// provide consistent mappings from string to hash accross versions of rook.
 func TruncateNodeName(format, nodeName string) string {
 	if len(nodeName)+len(fmt.Sprintf(format, "")) > validation.DNS1035LabelMaxLength {
 		hashed := Hash(nodeName)