feat: add auth model types (User, NKeyUser, Permissions) and auth config to NatsOptions

src/NATS.Server/NatsOptions.cs

@@ -1,3 +1,5 @@
+using NATS.Server.Auth;
+
 namespace NATS.Server;
 
 public sealed class NatsOptions
@@ -10,4 +12,19 @@ public sealed class NatsOptions
     public int MaxConnections { get; set; } = 65536;
     public TimeSpan PingInterval { get; set; } = TimeSpan.FromMinutes(2);
     public int MaxPingsOut { get; set; } = 2;
+
+    // Simple auth (single user)
+    public string? Username { get; set; }
+    public string? Password { get; set; }
+    public string? Authorization { get; set; }
+
+    // Multiple users/nkeys
+    public IReadOnlyList<User>? Users { get; set; }
+    public IReadOnlyList<NKeyUser>? NKeys { get; set; }
+
+    // Default/fallback
+    public string? NoAuthUser { get; set; }
+
+    // Auth timing
+    public TimeSpan AuthTimeout { get; set; } = TimeSpan.FromSeconds(1);
 }