Replace hardcoded string with constant

Author: scottaddie

samples/ClaimsTransformation/Controllers/AccountController.cs

@@ -2,6 +2,7 @@
 using System.Security.Claims;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.Cookies;
 using Microsoft.AspNetCore.Mvc;
 
 namespace AuthSamples.ClaimsTransformer.Controllers
@@ -36,7 +37,7 @@ public async Task<IActionResult> Login(string userName, string password, string
                     new Claim("role", "Member")
                 };
 
-                await HttpContext.SignInAsync(new ClaimsPrincipal(new ClaimsIdentity(claims, "Cookies", "user", "role")));
+                await HttpContext.SignInAsync(new ClaimsPrincipal(new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme, "user", "role")));
 
                 if (Url.IsLocalUrl(returnUrl))
                 {