store date when account is last seen

This date will be used to drop personal user data if the account is
inactive for a certain period.

The automatic personal user data clean up has been announced here:
https://linuxfr.org/news/regles-de-perennite-des-comptes-linuxfr-org-et-donnees-a-caractere-personnel

This commit only add a column on Account and do not add scheduled jobs
to apply deletion.

To avoid to update database too often and to avoid to keep too accurate
user personal information, only the date will be saved on database.

Suivi request to add this information into database:
https://linuxfr.org/suivi/pouvoir-determiner-si-un-compte-a-eu-de-l-activite-recemment

Author: Trim

app/controllers/application_controller.rb

@@ -5,6 +5,7 @@ class ApplicationController < ActionController::Base
   protect_from_forgery with: :reset_session, prepend: true
   before_action :seo_filter
   before_action :configure_permitted_parameters, if: :devise_controller?
+  before_action :set_account_last_seen, if: :account_signed_in?
   helper_method :url_for_content, :path_for_content, :current_user, :current_stylesheet
   rescue_from Canable::Transgression, with: :error_403
 
@@ -44,6 +45,15 @@ def seo_filter
     @dont_index    = params.has_key?(:order) || (request.headers["User-Agent"] =~ /AppEngine-Google/i)
   end
 
+  def set_account_last_seen
+    # Update last seen only once a day to avoid too many database update
+    if Date.today - current_account.last_seen_on >= 1
+      # Use update_columns to ensure updated_at value is not changed with this
+      # automatic update
+      current_account.update_columns(last_seen_on: Date.today);
+    end
+  end
+
   def dont_index?
     !!@dont_index
   end

db/migrate/20230506121910_add_last_seen_on_to_accounts.rb

@@ -0,0 +1,26 @@
+class AddLastSeenOnToAccounts < ActiveRecord::Migration[5.2]
+  def change
+    add_column :accounts, :last_seen_on, :date
+
+    reversible do |set_last_seen_on|
+      set_last_seen_on.up do
+        # Set default value only for confirmed accounts
+        execute <<-SQL
+          UPDATE accounts
+            SET last_seen_on =
+              CASE
+                WHEN confirmed_at is NULL
+                  THEN NULL
+                WHEN login in ("Anonyme", "Collectif")
+                  THEN NULL
+                ELSE
+                  CURRENT_DATE()
+                END
+        SQL
+      end
+      set_last_seen_on.down do
+        # Column will be dropped nothing to do
+      end
+    end
+  end
+end