Getting data from REST API using cpprestsdk

Question

I am following Pixabay API documentation to retrieve/download images. I don't have a lot of understanding of URI/REST/HTTP workings but I was able to follow some documentation and get boilerplate code:

int main()
{

    auto fileStream = std::make_shared<ostream>();

    //Open stream for output file
    pplx::task<void> requestTask = fstream::open_ostream("results.html")
    
    .then([=](ostream outFile) {
        http_client client("https://pixabay.com/");
        uri_builder builder("/api/");
        builder.append_query("key", "xxxxxxx-xxxxxx-xxxxxxx");
        builder.append_query("q", "yellow%20flowers");
        builder.append_query("image_type", "photo");
        std::cout << builder.to_string() << std::endl;
        return client.request(methods::GET, builder.to_string()); })

    // Handle the response headers arriving
    .then([=](http_response response) {
        printf("Received response status code: %u\n", response.status_code());
        return response.body().read_to_end(fileStream->streambuf()); })

    // Close the file stream.
    .then([=](size_t) { 
        return fileStream->close(); });


    // Wait for all the outstanding I/O to complete and handle any exceptions
    try {
        requestTask.wait();
    }
    catch (const std::exception &e) {
        printf("Exception: %s\n", e.what());
    }

    return 0;
}

Problem : This code always gives me status code 301. If I directly run https://pixabay.com/api/?key=xxxxxxx-xxxxxx-xxxxxxx&q=yellow+flowers&image_type=photo&pretty=true this link in the browser, I am getting the JSON data back. I am not sure if I am able to build this URI correctly through URI builder using the above code.

Some variation of the code that I tried involves commenting out query parameter q , removing/adding / from http_client/uri_builder but none of that worked.

Please help me understand what is the correct way of getting this done.

Thanks!