Issues with running the quickstart demo

[thinkcodellc]

This is the acs-ca-demo linked at https://techcommunity.microsoft.com/t5/azure-communication-services/build-2023-transforming-customer-experiences-with-automated-ai/ba-p/3827857

Branch -callautomation-openai-sample-csharp

This issue is for a: (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request
- [x ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

1. DevTunnels has an issue registering for event grid. Tried with ngrok and it seems to register.
2. Unable to get answer from Azure Cognitive Services for

 var options = new AnswerCallOptions(incomingCallContext, callbackUri)
       {
           AzureCognitiveServicesEndpointUrl = new Uri(cognitiveServicesEndpoint)
       };

       AnswerCallResult answerCallResult = await client.AnswerCallAsync(options);
       Console.WriteLine($"Answer call result: {answerCallResult.CallConnection.CallConnectionId}");

with error message

fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
      An unhandled exception has occurred while executing the request.
      Azure.RequestFailedException: Service Principal for the Azure Communication Service Resource is not configured.
      Status: 400 (Bad Request)
      ErrorCode: 8567

      Content:
      {"error":{"code":"8567","message":"Service Principal for the Azure Communication Service Resource is not configured."}}

Where do we add the Cognitive services multi-service account key for this access from the code?

Minimal steps to reproduce

Follow the readme guide

Any log messages given by the failure

fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
An unhandled exception has occurred while executing the request.
Azure.RequestFailedException: Service Principal for the Azure Communication Service Resource is not configured.
Status: 400 (Bad Request)
ErrorCode: 8567

  Content:
  {"error":{"code":"8567","message":"Service Principal for the Azure Communication Service Resource is not configured."}}

### Expected/desired behavior
> No trouble connecting devtunnels
and ability for cog svs to respond back for the incoming call?