Adds valid issuers for Tesla authentication

Adds multiple valid issuers to the authentication configuration.
This ensures compatibility with different Tesla authentication endpoints,
including fleet and regional variations.

Source/ProofOfConcept/Program.cs

@@ -55,6 +55,8 @@ builder.Services.AddAuthentication(o =>
 
     // This must match exactly what you register at Tesla
     o.CallbackPath = new PathString("/token-exchange");
+
+    o.TokenValidationParameters.ValidIssuers = ["https://fleet-auth.tesla.com/oauth2/v3/nts", "https://auth.tesla.com/oauth2/v3", "https://fleet-auth.prd.vn.cloud.tesla.com/oauth2/v3/nts"];
     
     // Scopes you actually need
     o.Scope.Clear();