protected override async Task <HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct)
{
// Get authorization token from Azure AD.
var authenticationResult = await _clientApplication.AcquireTokenForClientAsync(Scopes);
// Set authorization token on request.
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", authenticationResult.AccessToken);
return(await base.SendAsync(request, ct));
}