Fail closed on malformed local auth

JobTrackerApi/Services/CurrentUserService.cs

@@ -16,14 +16,5 @@ public sealed class CurrentUserService : ICurrentUserService
         _http = http;
     }
 
-    public string? UserId
-    {
-        get
-        {
-            var u = _http.HttpContext?.User;
-            if (u is null) return null;
-            if (u.Identity?.IsAuthenticated != true) return null;
-            return u.FindFirstValue(ClaimTypes.NameIdentifier) ?? u.FindFirstValue("sub");
-        }
-    }
+    public string? UserId => LocalAuthIdentity.GetRequiredUserId(_http.HttpContext?.User);
 }

JobTrackerApi/Services/LocalAuthIdentity.cs

@@ -0,0 +1,17 @@
+using System.Security.Claims;
+
+namespace JobTrackerApi.Services;
+
+public static class LocalAuthIdentity
+{
+    public static string? GetRequiredUserId(ClaimsPrincipal? user)
+    {
+        if (user?.Identity?.IsAuthenticated != true)
+        {
+            return null;
+        }
+
+        var userId = user.FindFirstValue(ClaimTypes.NameIdentifier) ?? user.FindFirstValue("sub");
+        return string.IsNullOrWhiteSpace(userId) ? null : userId;
+    }
+}