Shorten access token validity period

To prepare for login system migration.

lib/cadet_web/controllers/auth_controller.ex

@@ -162,7 +162,7 @@ defmodule CadetWeb.AuthController do
   @spec generate_tokens(User.t()) :: %{access_token: String.t(), refresh_token: String.t()}
   defp generate_tokens(user) do
     {:ok, access_token, _} =
-      Guardian.encode_and_sign(user, %{}, token_type: "access", ttl: {1, :hour})
+      Guardian.encode_and_sign(user, %{}, token_type: "access", ttl: {20, :minutes})
 
     {:ok, refresh_token, _} =
       Guardian.encode_and_sign(user, %{}, token_type: "refresh", ttl: {1, :week})