code: private static String getBase64EncodedString(String str) {
      ByteBuf byteBuf = null;
      ByteBuf encodedByteBuf = null;
      try {
        byteBuf = Unpooled.wrappedBuffer(str.getBytes(StandardCharsets.UTF_8));
        encodedByteBuf = Base64.encode(byteBuf);
        return encodedByteBuf.toString(StandardCharsets.UTF_8);
      } finally {
        // The release is called to suppress the memory leak error messages raised by netty.
        if (byteBuf != null) {
          byteBuf.release();
          if (encodedByteBuf != null) {
            encodedByteBuf.release();
          }
        }
      }
    }
docs: Return a Base64-encoded string.