value: String,
      ) = apply {
        names +=
          name.canonicalizeWithCharset(
            encodeSet = FORM_ENCODE_SET,
            // Plus is encoded as `%2B`, space is encoded as plus.
            plusIsSpace = false,
            charset = charset,
          )
        values +=
          value.canonicalizeWithCharset(
            encodeSet = FORM_ENCODE_SET,

 * @param unicodeAllowed true to leave non-ASCII codepoint unencoded.
 * @param charset which charset to use, null equals UTF-8.
 */
internal fun String.canonicalizeWithCharset(
  pos: Int = 0,
  limit: Int = length,
  encodeSet: String,
  alreadyEncoded: Boolean = false,
  strict: Boolean = false,
  plusIsSpace: Boolean = false,
  unicodeAllowed: Boolean = false,