updated tutorial (#637)

Co-authored-by: Benson Pan <[email protected]>

guides/tutorial/start-tutorial.md

@@ -102,7 +102,10 @@ defmodule AuthMe.UserManager.Guardian do
   end
 
   def resource_from_claims(%{"sub" => id}) do
-    UserManager.get_user!(id)
+    user = UserManager.get_user!(id)
+    {:ok, user}
+  rescue
+    e in Ecto.NoResultsError => {:error, :resource_not_found}
   end
 end
 ```
@@ -193,7 +196,7 @@ At this point, the autogenerated tests when we first created the UserManager and
 Fixing the broken tests is simple: we want to compare the encrypted passwords instead of plain text ones.
 
 ```elixir
-## test/auth_me/auth_test.exs
+## test/auth_me/user_manager_test.exs
 
 ...
 
@@ -294,17 +297,17 @@ defmodule AuthMeWeb.SessionController do
 
   def logout(conn, _) do
     conn
-    |> Guardian.Plug.sign_out() #This module's full name is Auth.UserManager.Guardian.Plug, 
+    |> Guardian.Plug.sign_out() #This module's full name is Auth.UserManager.Guardian.Plug,
     |> redirect(to: "/login")   #and the arguments specfied in the Guardian.Plug.sign_out()
-  end                           #docs are not applicable here               
+  end                           #docs are not applicable here
 
   defp login_reply({:ok, user}, conn) do
     conn
     |> put_flash(:info, "Welcome back!")
     |> Guardian.Plug.sign_in(user)   #This module's full name is Auth.UserManager.Guardian.Plug,
-    |> redirect(to: "/protected")    #and the arguments specified in the Guardian.Plug.sign_in() 
-  end                                #docs are not applicable here.                 
-                                               
+    |> redirect(to: "/protected")    #and the arguments specified in the Guardian.Plug.sign_in()
+  end                                #docs are not applicable here.
+
   defp login_reply({:error, reason}, conn) do
     conn
     |> put_flash(:error, to_string(reason))
@@ -441,5 +444,8 @@ Now exit iex and start up your server:
 $ mix phx.server
 ```
 
-Enter `localhost:4000/protected` in your browser's address bar, and you should see "unathenticated".  Now, enter `localhost:4000/login` in your browser's address bar, and login with your `me` username and `secret` password.  You should automatically be redirected to the protected page, which you can now see!  To logout, enter `localhost:4000/logout` in your browser's address bar, and you will be redirected to the login page.  Instead of logging in, enter `localhost:4000/protected` in your browser's address bar, and you will see "unathenticated" again!
-
+Enter `localhost:4000/protected` in your browser's address bar, and you should see "unauthenticated".
+Now, enter `localhost:4000/login` in your browser's address bar, and login with your `me` username and `secret` password.
+You should automatically be redirected to the protected page, which you can now see!
+To logout, enter `localhost:4000/logout` in your browser's address bar, and you will be redirected to the login page.
+Instead of logging in, enter `localhost:4000/protected` in your browser's address bar, and you will see "unauthenticated" again!