no inherite model, it is basic class

plain_model.rb

class PlainModel
  include ActiveModel::Model
  include ActiveSupport::Callbacks
  include ActiveModel::Validations::Callbacks
  
  define_callbacks :save
  
  def save 
    if valid?
      run_callbacks :save do 
    	true
      end
    else
      false 
    end
  end
end