docs: public static UnicodeFriendlyString unicodeFriendly(String utf16CodeUnits) {
      if (utf16CodeUnits.codePointCount(0, utf16CodeUnits.length()) == utf16CodeUnits.length()) {
        return StringWithoutNonBmp.of(utf16CodeUnits);
      } else {
        return StringWithNonBmp.of(utf16CodeUnits);
      }
    }