Add project files

T120B165-ImgBoard/Data/DbInitializer.cs

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+using Microsoft.AspNetCore.Identity;
+using T120B165_ImgBoard.Models;
+
+namespace T120B165_ImgBoard.Data;
+
+public static class DbInitializer
+{
+    public static async Task SeedRolesAsync(IServiceProvider serviceProvider)
+    {
+        var roleManager = serviceProvider.GetRequiredService<RoleManager<IdentityRole>>();
+        string[] roleNames = [UserRoles.Admin, UserRoles.Regular];
+        foreach (var roleName in roleNames)
+        {
+            if (!await roleManager.RoleExistsAsync(roleName))
+            {
+                await roleManager.CreateAsync(new IdentityRole(roleName));
+            }
+        }
+    }
+}