feat: implement Stripe product configuration and add token-based input validation using Microsoft.ML.Tokenizers

src/NexusReader.Infrastructure/Configuration/StripeSettings.cs

@@ -0,0 +1,9 @@
+namespace NexusReader.Infrastructure.Configuration;
+
+public record StripeSettings
+{
+    public const string SectionName = "Stripe";
+    public string ProProductId { get; init; } = string.Empty;
+    public string BasicProductId { get; init; } = string.Empty;
+    public string FreeProductId { get; init; } = string.Empty;
+}