Cosmos extensions for the server

CosmosExtensions.cs

using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;
using IdentityServer4.Extensions;
using Microsoft.AspNetCore.Identity;
using BlazorCosmosWasm.Server.Models;
using Microsoft.Azure.Cosmos;
using Microsoft.Extensions.Configuration;

namespace BlazorCosmosWasm.Server.Controllers
{
    public static class CosmosExtensions
    {
        public async static Task<string> GetEmailAsync(this ClaimsPrincipal user, UserManager<ApplicationUser> userManager)
        {
            if (user.IsAuthenticated())
            {
                var id = user.Claims.SingleOrDefault(
                    key => key.Type == ClaimTypes.NameIdentifier)?.Value;
                var appUser = await userManager.FindByIdAsync(id);
                return appUser?.Email;
            }
            return null;
        }

        public static CosmosClient CreateCosmosClientFromConfig(this IConfiguration config)
        {
            return new CosmosClient(config.GetValue<string>("CosmosConnection"));
        }

    }
}