Track last sign in date (#553)

* add trackable module to devise

* disable IP adress logging in trackable module of devise

* extend comment to explain better what happens

* remove redundant lines in comment

app/models/user.rb

@@ -3,7 +3,7 @@ class User < ApplicationRecord
   include ApplicationHelper
 
   # use devise for authentification, include the following modules
-  devise :database_authenticatable, :registerable,
+  devise :database_authenticatable, :registerable, :trackable,
          :recoverable, :rememberable, :validatable, :confirmable, :lockable
 
   # a user has many subscribed lectures
@@ -751,6 +751,21 @@ def can_update_personell?(lecture)
     return false
   end
 
+  # see https://github.com/heartcombo/devise/issues/4849#issuecomment-534733131
+  # We use the Devise::Trackable module to track sign-in count and current/last
+  # sign-in timestamp. However, we don't want to track IP address, but Trackable
+  # tries to, so we have to manually override the accessor methods so they do
+  # nothing.
+
+  def current_sign_in_ip
+  end
+
+  def last_sign_in_ip=(_ip)
+  end
+
+  def current_sign_in_ip=(_ip)
+  end
+
   private
 
     def set_defaults

db/migrate/20231101100015_add_devise_trackable_columns_to_users.rb

@@ -0,0 +1,9 @@
+class AddDeviseTrackableColumnsToUsers < ActiveRecord::Migration[7.0]
+  def change
+    add_column :users, :sign_in_count, :integer, default: 0, null: false
+    add_column :users, :current_sign_in_at, :datetime
+    add_column :users, :last_sign_in_at, :datetime
+    add_column :users, :current_sign_in_ip, :string
+    add_column :users, :last_sign_in_ip, :string
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_04_27_124337) do
+ActiveRecord::Schema[7.0].define(version: 2023_11_01_100015) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -848,6 +848,11 @@
     t.datetime "locked_at", precision: nil
     t.text "image_data"
     t.string "ghost_hash"
+    t.integer "sign_in_count", default: 0, null: false
+    t.datetime "current_sign_in_at"
+    t.datetime "last_sign_in_at"
+    t.string "current_sign_in_ip"
+    t.string "last_sign_in_ip"
     t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
     t.index ["email"], name: "index_users_on_email", unique: true
     t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true