raw_binary_transcoder should be accepted by all get_result::content_as overloads

    template<typename Document,

             typename Transcoder = codec::default_json_transcoder,

             std::enable_if_t<!codec::is_transcoder_v<Document>, bool> = true,

             std::enable_if_t<codec::is_transcoder_v<Transcoder>, bool> = true>

    [[nodiscard]] auto content_as() const -> Document