*/
fun X509Certificate.certificatePem(): String =
  buildString {
    append("-----BEGIN CERTIFICATE-----\n")
    encodeBase64Lines(encoded.toByteString())
    append("-----END CERTIFICATE-----\n")
  }

internal fun StringBuilder.encodeBase64Lines(data: ByteString) {
  val base64 = data.base64()
  for (i in 0 until base64.length step 64) {
    append(base64, i, minOf(i + 64, base64.length)).append('\n')

   * [rfc_7468]: https://tools.ietf.org/html/rfc7468
   */
  fun privateKeyPkcs8Pem(): String =
    buildString {
      append("-----BEGIN PRIVATE KEY-----\n")
      encodeBase64Lines(keyPair.private.encoded.toByteString())
      append("-----END PRIVATE KEY-----\n")
    }

  /**
   * Returns the RSA private key encoded in [PKCS #1][rfc_8017] [PEM format][rfc_7468].
   *