Update the Identity chapter to change register behavior

[AdamSheaffer]

This is, in part, a research ticket. I'm not sure if this is necessary, but I just recently created a new project using Identity for the first time since upgrading to 3.0 and the default register page wants you to set up email verification of your users' email addresses--Submitting the register form now seems to bring you to a view that suggests you (the developer) should set up an IEmailSender service for email verification. Here is the code I ran into in OnPostAsync

                if (result.Succeeded)
                {
                    _logger.LogInformation("User created a new account with password.");

                    var code = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                    code = WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(code));
                    var callbackUrl = Url.Page(
                        "/Account/ConfirmEmail",
                        pageHandler: null,
                        values: new { area = "Identity", userId = user.Id, code = code },
                        protocol: Request.Scheme);

                    await _emailSender.SendEmailAsync(Input.Email, "Confirm your email",
                        $"Please confirm your account by <a href='{HtmlEncoder.Default.Encode(callbackUrl)}'>clicking here</a>.");

                    if (_userManager.Options.SignIn.RequireConfirmedAccount)
                    {
                        return RedirectToPage("RegisterConfirmation", new { email = Input.Email });
                    }
                    else
                    {
                        await _signInManager.SignInAsync(user, isPersistent: false);
                        return LocalRedirect(returnUrl);
                    }
                }
                foreach (var error in result.Errors)
                {
                    ModelState.AddModelError(string.Empty, error.Description);
                }

I suggest this edit, but this might be something worth further consideration. Maybe you do actually want to set up an email verification system?

                if (result.Succeeded)
                {
                    _logger.LogInformation("User created a new account with password.");

                    await _signInManager.SignInAsync(user, isPersistent: false);
                    return LocalRedirect(returnUrl);
                }
                foreach (var error in result.Errors)
                {
                    ModelState.AddModelError(string.Empty, error.Description);
                }