Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace backend
{
    public class Startup
    {
        public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            string connectionString = Configuration.GetConnectionString("DefaultConnection");
            services.AddDbContext<ApplicationDbContext>(options => options.UseSqlite(connectionString));
            services.AddSpaStaticFiles(configuration: options => { options.RootPath = "wwwroot"; });
            services.AddControllers();
            services.AddCors(options =>
            {
                options.AddPolicy("VueCorsPolicy", builder =>
                {
                    builder
                    .AllowAnyHeader()
                    .AllowAnyMethod()
                    .AllowCredentials()
                    .WithOrigins("https://localhost:5001");
                });
            });
            services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
  .AddJwtBearer(options =>
                {
                    options.Authority = Configuration["Okta:Authority"];
                    options.Audience = "api://default";
                });
            services.AddMvc(option => option.EnableEndpointRouting = false);
        }

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

            app.UseCors("VueCorsPolicy");

            dbContext.Database.EnsureCreated();
            app.UseAuthentication();
            app.UseMvc();
            app.UseRouting();
            app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
            app.UseSpaStaticFiles();
            app.UseSpa(configuration: builder =>
            {
                if (env.IsDevelopment())
                {
                    builder.UseProxyToSpaDevelopmentServer("http://localhost:8080");
                }
            });
        }
    }
}