astuto/app/models/user.rb

class User < ApplicationRecord
  enum role: [:user, :moderator, :admin]
  after_initialize :set_default_role, if: :new_record?

  def set_default_role
    self.role ||= :user
  end

  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable,
         :confirmable
end