code: public String getResponseBodyAsString() {
          final ByteBuf bodyByteBuf = httpInputMessage.getBody();
          final String contentEncoding = httpInputMessage.getHeaders().get(HttpHeaders.CONTENT_ENCODING);
          byte[] bytes = new byte[bodyByteBuf.readableBytes()];
          bodyByteBuf.readBytes(bytes);
          return new String(bytes, contentEncoding != null ? Charset.forName(contentEncoding) : Charset.forName(DEFAULT_CHARSET));
      }
docs: Return the response body as a string.
  
  @since 3.0.5