ectomobile/app/models/user.rb

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  devise :database_authenticatable,
         :recoverable, :rememberable, :validatable, :lockable, :timeoutable

  # Trazabilidad
  #
  # @see {https://guides.rubyonrails.org/association_basics.html#self-joins}
  belongs_to :created_by, class_name: 'User', optional: true
  has_many :created, class_name: 'User', foreign_key: 'created_by_id'
end