add convert string

yaml/converter/convert_oss.go

@@ -21,3 +21,9 @@ package converter
 func Convert(d []byte, m Metadata) ([]byte, error) {
 	return d, nil
 }
+
+// ConvertString converts the yaml configuration file from
+// the legacy format to the 1.0+ format.
+func ConvertString(s string, m Metadata) (string, error) {
+	return s, nil
+}