Managed Identity Support #234

    var factory = new AzureIdentityOrgSvcFactory(new ("https://....dynamics.com"), new Azure.Identity.DefaultAzureCredential(), logger);

    class AzureIdentityOrgSvcFactory : IOrganizationServiceFactory
    {
        readonly Uri uri;
        readonly TokenCredential tokenCredential;
        readonly ILogger logger;

        public OrgSvcFactory(Uri uri, TokenCredential tokenCredential, ILogger logger)
        {
            this.logger = logger;
            this.uri = uri;
            this.tokenCredential = tokenCredential;
        }

        public IOrganizationService CreateOrganizationService(Guid? userId)
        {
            var c = new Microsoft.PowerPlatform.Dataverse.Client.ServiceClient(uri, GetToken, logger: logger);

            if (userId is Guid callerId)
                c.CallerId = callerId;

            return c;
        }

        async Task<string> GetToken(string instance)
        {
            var option = new TokenRequestContext(new[] { uri.AbsoluteUri + ".default" });
            var token = await tokenCredential.GetTokenAsync(option, default);
            return token.Token;
        }
    }