(Unicode C++) Auth0 Server-to-Server Access Token (Client Credentials flow)

Demonstrates how to obtain an Auth0 access token using client credentials (client_id and client_secret).

This is just a matter of duplicating this CURL command:

curl --request POST
  --url 'https://chilkat.auth0.com/oauth/token' \
  --header 'content-type: application/json' \
  --data '{"grant_type":"client_credentials","client_id": "xxxx","client_secret": "xxxx","audience": "https://api.example.com/geocoding/v1/"}'

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#include <CkJsonObjectW.h>
#include <CkHttpW.h>
#include <CkHttpResponseW.h>

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

    // We want to duplicate this curl command:
    // 
    // curl --request POST
    //   --url 'https://chilkat.auth0.com/oauth/token' \
    //   --header 'content-type: application/json' \
    //   --data '{"grant_type":"client_credentials","client_id": "my_client_id","client_secret": "my_client_secret","audience": "https://api.example.com/geocoding/v1/"}'

    // Build the JSON body of the request.
    CkJsonObjectW json;
    json.UpdateString(L"grant_type",L"client_credentials");
    json.UpdateString(L"client_id",L"AUTH0-CLIENT-ID");
    json.UpdateString(L"client_secret",L"AUTH0-CLIENT-SECRET");
    json.UpdateString(L"audience",L"https://api.example.com/geocoding/v1/");

    // IMPORTANT: You would use your own url.  You would not use "chilkat.auth0.com".  
    // Instead you would use "your_name.auth0.com"
    CkHttpW http;
    CkHttpResponseW *resp = http.PostJson3(L"https://chilkat.auth0.com/oauth/token",L"application/json",json);
    if (http.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",http.lastErrorText());
        return;
    }

    // A 200 response status code indicates success.  In the success case, the response body
    // contains the JSON access token, such as: 
    // {
    //   "access_token": "eyJz93a...k4laUWw",
    //   "token_type":"Bearer",
    //   "expires_in":86400
    // }
    // 

    wprintf(L"response status code = %d\n",resp->get_StatusCode());

    // The repsonse is JSON if successful and also JSON for errors.
    CkJsonObjectW jsonResp;
    jsonResp.put_EmitCompact(false);
    jsonResp.Load(resp->bodyStr());

    if (resp->get_StatusCode() != 200) {
        // The response body contains error information in JSON format.
        wprintf(L"%s\n",jsonResp.emit());
        delete resp;

        // An example of an error response:
        // 		{
        // 		  "error": "access_denied",
        // 		  "error_description": "Client is not authorized to access \"https://api.example.com/geocoding/v1/\". You might probably want to create a \"client-grant\" associated to this API. See: https://auth0.com/docs/api/v2#!/Client_Grants/post_client_grants"
        // 		}
        return;
    }

    wprintf(L"Success!\n");
    wprintf(L"%s\n",jsonResp.emit());

    // A successful JSON response body looks like this:

    // {
    //   "access_token": "eyJz93a...k4laUWw",
    //   "token_type":"Bearer",
    //   "expires_in":86400
    // }

    delete resp;
    }