Startup.cs

using System;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Opifex.Rsvp.Data;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.AspNetCore.Identity.UI.Services;
using SendGrid.Extensions.DependencyInjection;
using Microsoft.AspNetCore.Authentication.Cookies;

namespace Opifex.Rsvp
{
    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.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(
                    Configuration.GetConnectionString("DefaultConnection")));

            services.AddIdentity<ApplicationUser, ApplicationRole>(options =>
            {
                options.SignIn.RequireConfirmedAccount = false;
                options.User.RequireUniqueEmail = true;
                options.Password.RequiredLength = 12;
                options.Password.RequiredUniqueChars = 4;
                options.Password.RequireDigit = false;
                options.Password.RequireLowercase = false;
                options.Password.RequireNonAlphanumeric = false;
                options.Password.RequireUppercase = false;
            })
                .AddEntityFrameworkStores<ApplicationDbContext>()
                .AddDefaultTokenProviders();

            services.ConfigureApplicationCookie(options =>
            {
                options.AccessDeniedPath = "/Identity/Account/AccessDenied";
                options.Cookie.Name = "OpifexRsvp";
                options.Cookie.HttpOnly = true;
                options.ExpireTimeSpan = TimeSpan.FromMinutes(60);
                options.LoginPath = "/Identity/Account/Login";
                options.ReturnUrlParameter = CookieAuthenticationDefaults.ReturnUrlParameter;
                options.SlidingExpiration = true;
            });

            services.AddRazorPages();
            
            services.AddSendGrid(options =>
            {
                options.ApiKey =
                    Environment.GetEnvironmentVariable("SENDGRID_API_KEY")
                        ?? Configuration["SendGrid:ApiKey"];
            });

            services.AddSingleton<IEmailSender, EmailSender>();
        }

        // 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.UseDatabaseErrorPage();
            }
            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.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthentication();
            app.UseAuthorization();

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