Update content-language field for Azure gateway (#6061)

Fixes https://github.com/minio/minio-go/issues/996

cmd/gateway/azure/gateway-azure.go

@@ -238,6 +238,8 @@ func s3MetaToAzureProperties(ctx context.Context, s3Metadata map[string]string)
 			props.ContentMD5 = v
 		case k == "Content-Type":
 			props.ContentType = v
+		case k == "Content-Language":
+			props.ContentLanguage = v
 		}
 	}
 	return blobMeta, props, nil
@@ -292,6 +294,9 @@ func azurePropertiesToS3Meta(meta storage.BlobMetadata, props storage.BlobProper
 	if props.ContentType != "" {
 		s3Metadata["Content-Type"] = props.ContentType
 	}
+	if props.ContentLanguage != "" {
+		s3Metadata["Content-Language"] = props.ContentLanguage
+	}
 	return s3Metadata
 }