code: private static ByteBuf createSettingsFrame(ChannelHandlerContext ctx, ByteBuf payload) {
          ByteBuf frame = ctx.alloc().buffer(FRAME_HEADER_LENGTH + payload.readableBytes());
          writeFrameHeader(frame, payload.readableBytes(), SETTINGS, new Http2Flags(), 0);
          frame.writeBytes(payload);
          payload.release();
          return frame;
      }
docs: Creates an HTTP2-Settings header with the given payload. The payload buffer is released.