Add remember-me function for sign-in

When checked, remember user for 2 weeks. Otherwise expire session after
30 minutes.

db/migrate/20230319101128_add_remember_created_at_to_users.rb

@@ -0,0 +1,6 @@
+class AddRememberCreatedAtToUsers < ActiveRecord::Migration[7.0]
+  def change
+    add_column :users, :remember_created_at, :datetime
+    add_column :users, :remember_token, :string
+  end
+end