Enable devise lockable module with default values

In order to the display a warn text on the last attempt
before the account is locked, we need update
config.paranoid to false as the devise documentation
explains.

Adding "config.paranoid: false" implies further changes
to the code, so for now we unncomment the default value
"config.last_attempt_warning = true" and update it to false.

db/migrate/20231009073912_add_lockable_to_devise.rb

@@ -0,0 +1,11 @@
+class AddLockableToDevise < ActiveRecord::Migration[6.1]
+  def change
+    # Only if lock strategy is :failed_attempts
+    add_column :users, :failed_attempts, :integer, default: 0, null: false
+    add_column :users, :locked_at, :datetime
+
+    # Add these only if unlock strategy is :email or :both
+    add_column :users, :unlock_token, :string
+    add_index :users, :unlock_token, unique: true
+  end
+end

db/schema.rb

@@ -1644,6 +1644,9 @@ ActiveRecord::Schema.define(version: 2023_10_12_141318) do
     t.boolean "recommended_debates", default: true
     t.boolean "recommended_proposals", default: true
     t.string "subscriptions_token"
+    t.integer "failed_attempts", default: 0, null: false
+    t.datetime "locked_at"
+    t.string "unlock_token"
     t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
     t.index ["date_of_birth"], name: "index_users_on_date_of_birth"
     t.index ["email"], name: "index_users_on_email", unique: true
@@ -1652,6 +1655,7 @@ ActiveRecord::Schema.define(version: 2023_10_12_141318) do
     t.index ["hidden_at"], name: "index_users_on_hidden_at"
     t.index ["password_changed_at"], name: "index_users_on_password_changed_at"
     t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
+    t.index ["unlock_token"], name: "index_users_on_unlock_token", unique: true
     t.index ["username"], name: "index_users_on_username"
   end