feat: implement identity authentication, authorization policies, and MAUI platform support with Docker orchestration

src/NexusReader.Infrastructure/Services/BillingService.cs

@@ -0,0 +1,53 @@
+using Microsoft.AspNetCore.Identity;
+using Microsoft.EntityFrameworkCore;
+using NexusReader.Application.Abstractions.Services;
+using NexusReader.Domain.Entities;
+using NexusReader.Infrastructure.Persistence;
+
+namespace NexusReader.Infrastructure.Services;
+
+public class BillingService : IBillingService
+{
+    private readonly AppDbContext _dbContext;
+    private readonly UserManager<NexusUser> _userManager;
+
+    public BillingService(AppDbContext dbContext, UserManager<NexusUser> userManager)
+    {
+        _dbContext = dbContext;
+        _userManager = userManager;
+    }
+
+    public async Task<bool> HandleSubscriptionUpdatedAsync(string customerEmail, string stripeProductId)
+    {
+        var user = await _userManager.FindByEmailAsync(customerEmail);
+        if (user == null) return false;
+
+        // Map Stripe Product IDs to Nexus Plans
+        // These IDs would typically come from configuration
+        if (stripeProductId.Contains("pro")) 
+        {
+            user.CurrentPlan = "Pro";
+            user.AITokenLimit = 50000;
+        }
+        else if (stripeProductId.Contains("basic"))
+        {
+            user.CurrentPlan = "Basic";
+            user.AITokenLimit = 10000;
+        }
+
+        await _userManager.UpdateAsync(user);
+        return true;
+    }
+
+    public async Task<bool> HandleSubscriptionDeletedAsync(string customerEmail)
+    {
+        var user = await _userManager.FindByEmailAsync(customerEmail);
+        if (user == null) return false;
+
+        user.CurrentPlan = "Free";
+        user.AITokenLimit = 1000; // Reset to free limit
+        
+        await _userManager.UpdateAsync(user);
+        return true;
+    }
+}