Apply suggestions from code review

Co-authored-by: Kevin B <[email protected]>

Author: BenjaminMichaelis

EssentialCSharp.Web/Middleware/ReferralTrackingMiddleware.cs

@@ -7,7 +7,7 @@
 
 namespace EssentialCSharp.Web.Middleware;
 
-public class ReferralMiddleware
+public sealed class ReferralMiddleware
 {
     private readonly RequestDelegate _Next;
 
@@ -23,7 +23,7 @@ public async Task InvokeAsync(HttpContext context, IReferralService referralServ
         string? referralId = query["rid"];
         string? userReferralId;
 
-        if (context.User is { } claimsUser && claimsUser.Identity is not null && claimsUser.Identity.IsAuthenticated)
+        if (context.User is { Identity.IsAuthenticated: true } claimsUser)
         {
             if (!string.IsNullOrWhiteSpace(referralId))
             {

EssentialCSharp.Web/Services/ReferralService.cs

@@ -25,7 +25,7 @@ public class ReferralService(EssentialCSharpWebContext dbContext, SqidsEncoder<i
             }
             else
             {
-                Random random = new();
+                Random random = Random.Shared;
                 string referrerId = sqids.Encode(random.Next());
                 user.ReferrerId = referrerId;