fix: use equalFold() instead of lower and compare (#13624)

cmd/disk-cache-utils.go

@@ -110,7 +110,7 @@ func cacheControlOpts(o ObjectInfo) *cacheControl {
 
 	var headerVal string
 	for k, v := range m {
-		if strings.ToLower(k) == "cache-control" {
+		if strings.EqualFold(k, "cache-control") {
 			headerVal = v
 		}
 

cmd/warm-backend-azure.go

@@ -47,7 +47,7 @@ func (az *warmBackendAzure) getDest(object string) string {
 }
 func (az *warmBackendAzure) tier() azblob.AccessTierType {
 	for _, t := range azblob.PossibleAccessTierTypeValues() {
-		if strings.ToLower(az.StorageClass) == strings.ToLower(string(t)) {
+		if strings.EqualFold(az.StorageClass, string(t)) {
 			return t
 		}
 	}