Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.SpaServices.ReactDevelopmentServer;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Okta.AspNetCore;

namespace budgeteer
{
    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)
        {
            services.AddSwaggerDocument();

            services.Configure<PlaidSettings>(Configuration.GetSection("Plaid"));

            services.AddHttpClient<IPlaidService, PlaidService>();
            services.AddHttpContextAccessor();

            services.AddMvc().AddNewtonsoftJson();

            services.AddDbContext<PlaidContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("PlaidDatabase")));

            services.AddAuthentication(options =>
            {
                options.DefaultAuthenticateScheme = OktaDefaults.ApiAuthenticationScheme;
                options.DefaultChallengeScheme = OktaDefaults.ApiAuthenticationScheme;
                options.DefaultSignInScheme = OktaDefaults.ApiAuthenticationScheme;
            })
            .AddOktaWebApi(new OktaWebApiOptions()
            {
                OktaDomain = Configuration["Okta:OktaDomain"],
            });

            services.AddAuthorization();

            services.AddCors(options =>
            {
                // The CORS policy is open for testing purposes. In a production application, you should restrict it to known origins.
                options.AddPolicy(
                    "AllowAll",
                    builder => builder.AllowAnyOrigin()
                                    .AllowAnyMethod()
                                    .AllowAnyHeader());
            });

            services.AddControllersWithViews();

            // In production, the React files will be served from this directory
            services.AddSpaStaticFiles(configuration =>
            {
                configuration.RootPath = "ClientApp/build";
            });

        }

        // 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();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            app.UseOpenApi(); // serve documents (same as app.UseSwagger())
            app.UseSwaggerUi3(); // serve Swagger UI

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseSpaStaticFiles();

            app.UseRouting();

            app.UseAuthentication();

            app.UseAuthorization();

            app.UseCors();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller}/{action=Index}/{id?}");
            });

            app.UseSpa(spa =>
            {
                spa.Options.SourcePath = "ClientApp";

                if (env.IsDevelopment())
                {
                    spa.UseReactDevelopmentServer(npmScript: "start");
                }
            });
        }
    }
}