[Bug] Meu projeto não está gerando a migration do UsuarioApi

Quando vou gerar a migration do UsuarioApi ocorre o erro abaixo na imagem.

using FilmesApi.Data;
using FilmesApi.Services;
using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
using UsuariosApi.Data;

namespace UsuariosApi
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {

            var connectionString = Configuration.GetConnectionString("UsuariosConnection");
            services.AddDbContext<AppDbContext>(opts => opts.UseSqlServer(connectionString));
            services.AddIdentity<IdentityUser<int>, IdentityRole<int>>()
                .AddEntityFrameworkStores<UserDbContext>();
            services.AddControllers();
            services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });
}