Error during sending a signed http request to ElasticSearch

hey,
I am running into an error while making a httprequest to Elastic Search The error is

> The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method

Following is the code. Any pointers to bug in my code or library would be appreciated.

```
`invocation_response my_handler(invocation_request const& request)
{
ClientConfiguration config;
config.region = Aws::Environment::GetEnv("AWS_REGION");
config.caFile = "/etc/pki/tls/certs/ca-bundle.crt";
auto credentialsProvider = Aws::MakeShared("es");

auto client = CreateHttpClient(config);
auto httpRequest = CreateHttpRequest(URL, HttpMethod::HTTP_GET,
Aws::Utils::Stream::DefaultResponseStreamFactoryMethod);

httpRequest->SetContentType("application/json");

nlohmann::json query1 = {};
query1.emplace("size", 25);

std::shared_ptr sstream = make_shared();
*sstream << query1;
httpRequest->AddContentBody(sstream);
Aws::Client::AWSAuthV4Signer signer(credentialsProvider, "es", config.region);
auto req = httpRequest.get();
signer.SignRequest(*req);
auto outcome = client->MakeRequest(httpRequest);
if (outcome->GetResponseCode() == HttpResponseCode::OK) {
cout << "SUCCESS" << endl;
} else {
// print the response from the http request
cout << "ERROR" << endl;
cout << outcome->GetResponseBody().rdbuf() << endl;
cout << outcome->GetResponseCode() << endl;

}`

```

Issueに示されているリクエストの構築と Aws::Client::AWSAuthV4Signer::SignRequest の呼び出しから始め、設定されたリージョンと環境認証情報を使用して Elasticsearch に対するリクエストを再現します。署名の入力値とサービスのレスポンスを比較します。ライブラリの不具合を最小限の再現で確認するか、呼び出し側の設定の修正を文書化できれば完了です。

索引モデルが issue の本文から書いたものです。