feat: add application preloader, identity roles, and resilient database initialization with automated seeding

src/NexusReader.Infrastructure/Persistence/DbInitializer.cs

@@ -0,0 +1,72 @@
+using Microsoft.AspNetCore.Identity;
+using Microsoft.Extensions.DependencyInjection;
+using NexusReader.Domain.Entities;
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace NexusReader.Infrastructure.Persistence;
+
+public static class DbInitializer
+{
+    public static async Task SeedAsync(IServiceProvider serviceProvider)
+    {
+        using var scope = serviceProvider.CreateScope();
+        var userManager = scope.ServiceProvider.GetRequiredService<UserManager<NexusUser>>();
+        var roleManager = scope.ServiceProvider.GetRequiredService<RoleManager<IdentityRole>>();
+
+        try
+        {
+            Console.WriteLine("[Seeder] Starting database seeding...");
+
+            // Seed Roles
+            string[] roleNames = { "Admin", "User" };
+            foreach (var roleName in roleNames)
+            {
+                var roleExist = await roleManager.RoleExistsAsync(roleName);
+                if (!roleExist)
+                {
+                    await roleManager.CreateAsync(new IdentityRole(roleName));
+                    Console.WriteLine($"[Seeder] Created role: {roleName}");
+                }
+            }
+
+            // Seed Admin User
+            var adminEmail = "admin@nexus.com";
+            var adminUser = await userManager.FindByEmailAsync(adminEmail);
+
+            if (adminUser == null)
+            {
+                adminUser = new NexusUser
+                {
+                    UserName = adminEmail,
+                    Email = adminEmail,
+                    EmailConfirmed = true,
+                    CurrentPlan = "Enterprise",
+                    AITokenLimit = 1000000,
+                    TenantId = Guid.NewGuid()
+                };
+
+                var createPowerUser = await userManager.CreateAsync(adminUser, "Admin123!");
+                if (createPowerUser.Succeeded)
+                {
+                    await userManager.AddToRoleAsync(adminUser, "Admin");
+                    Console.WriteLine($"[Seeder] Admin user created successfully: {adminEmail}");
+                }
+                else
+                {
+                    var errors = string.Join(", ", createPowerUser.Errors.Select(e => e.Description));
+                    Console.WriteLine($"[Seeder] Failed to create admin user: {errors}");
+                }
+            }
+            else
+            {
+                Console.WriteLine("[Seeder] Admin user already exists.");
+            }
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"[Seeder] Critical error during seeding: {ex.Message}");
+        }
+    }
+}