private static void writeToFile(String path, Password... entries) throws IOException {
        try (FileOutputStream out = new FileOutputStream(path)) {
            for (Password entry: entries) {
                out.write(entry.value().getBytes(StandardCharsets.UTF_8));
            }
        }
    }
Creates a keystore with a single key and saves it to a file.

@param filename String file to save
@param password String store password to set on keystore
@param keyPassword String key password to set on key
@param alias String alias to use for the key
@param privateKey Key to save in keystore
@param cert Certificate to use as certificate chain associated to key
@throws GeneralSecurityException for any error with the security APIs
@throws IOException if there is an I/O error saving the file
clients/src/test/java/org/apache/kafka/test/TestSslUtils.java