Kayori_Medusa.net/Core/Server/AppDbConetext.cs

using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using Server.Entities;
using System;

namespace Server
{
    public class AppDbContext(DbContextOptions<AppDbContext> options)
    : IdentityDbContext<User, IdentityRole<int>, int>(options)
    {
        public override DbSet<User> Users { get; set; }
        public DbSet<Card> Cards { get; set; }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            builder.Entity<User>()
                .HasMany(u => u.Cards)
                .WithOne(c => c.User)
                .HasForeignKey(c => c.UserId)
                .OnDelete(DeleteBehavior.Cascade);

            base.OnModelCreating(builder);
        }
    }
}