Get bearier token for Azure Graph api

ktchoumak 

I do not understand why Microsoft using such low informative way in it's snippets?

https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/wiki/Client-credential-flows

Here is main wrapper:

        private static async Task<AuthenticationResult> GetToken(string tenantId, string appId, string clientSecret)
        {
            // this object will cache tokens in-memory - keep it as a singleton
            var singletonApp = ConfidentialClientApplicationBuilder.Create(appId)
                .WithClientSecret(clientSecret)
                .Build();

            // If instead you need to re-create the ConfidentialClientApplication on each request, you MUST customize 
            // the cache serialization (see below)

            // when making the request, specify the tenanted authority
            // uses the token cache automatically, which is optimized for multi-tenant access
            var authResult = await singletonApp.AcquireTokenForClient(scopes: new[] { "https://graph.microsoft.com/.default" })
                .WithAuthority(AzureCloudInstance.AzurePublic, tenantId)  // do not use "common" or "organizations"!
                .ExecuteAsync();

            return authResult;
        }