(C++) Azure AD Service-to-service access token request

Send an Azure AD service-to-service token request to get an access token using a shared secret.

For more information, see https://docs.microsoft.com/en-us/azure/active-directory/develop/v1-oauth2-client-creds-grant-flow#service-to-service-access-token-request

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#include <CkHttp.h>
#include <CkHttpRequest.h>
#include <CkHttpResponse.h>
#include <CkJsonObject.h>

void ChilkatSample(void)
    {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkHttp http;

    // To see the exact HTTP request sent and the response, set the SessionLogFilename property:
    http.put_SessionLogFilename("qa_output/chilkatHttpLog.txt");

    CkHttpRequest req;

    // Set the following request params:
    // grant_type 	required 	Specifies the requested grant type. In a Client Credentials Grant flow, the value must be client_credentials.
    // 
    // client_id 	required 	Specifies the Azure AD client id of the calling web service. 
    //     To find the calling application's client ID, in the Azure portal, click Azure Active Directory, click App registrations, click the application. 
    //     The client_id is the Application ID
    // 
    // client_secret 	required 	Enter a key registered for the calling web service or daemon application in Azure AD. 
    //     To create a key, in the Azure portal, click Azure Active Directory, click App registrations, click the application, click Settings, click Keys, and add a Key.
    //     URL-encode this secret when providing it.
    // 
    // resource 	required 	Enter the App ID URI of the receiving web service. To find the App ID URI, in the Azure portal, click Azure Active Directory, 
    //     click App registrations, click the service application, and then click Settings and Properties.

    req.AddParam("grant_type","client_credentials");
    req.AddParam("client_id","MY_CLIENT_ID");
    req.AddParam("client_secret","MY_CLIENT_SECRET");
    req.AddParam("resource","https://service.contoso.com/");

    // The URL passed to PostUrlEncoded has this form:   https://login.microsoftonline.com/<tenant_id>/oauth2/token
    CkHttpResponse *resp = http.PostUrlEncoded("https://login.microsoftonline.com/<tenant_id>/oauth2/token",req);
    if (http.get_LastMethodSuccess() == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    int respStatusCode = resp->get_StatusCode();
    std::cout << "Response Status Code = " << respStatusCode << "\r\n";

    CkJsonObject json;
    json.put_EmitCompact(false);
    json.Load(resp->bodyStr());
    std::cout << "Response JSON:" << "\r\n";
    std::cout << json.emit() << "\r\n";

    if (respStatusCode >= 400) {
        std::cout << "Response Header:" << "\r\n";
        std::cout << resp->header() << "\r\n";
        std::cout << "Failed." << "\r\n";
        delete resp;
        return;
    }

    // Sample response:

    // {
    //   "token_type": "Bearer",
    //   "expires_in": "3599",
    //   "ext_expires_in": "3599",
    //   "expires_on": "1570059833",
    //   "not_before": "1570055933",
    //   "resource": "https://adminchilkatsoft.onmicrosoft.com/eb1b8ced-76b7-4845-aec5-d3e91776e345",
    //   "access_token": "eyJ0eXAiO ... pmgw"
    // }

    // To get the items from the JSON....
    const char *token_type = json.stringOf("token_type");
    const char *expires_in = json.stringOf("expires_in");
    const char *ext_expires_in = json.stringOf("ext_expires_in");
    const char *expires_on = json.stringOf("expires_on");
    const char *not_before = json.stringOf("not_before");
    const char *resource = json.stringOf("resource");
    const char *access_token = json.stringOf("access_token");

    delete resp;
    }