customise devise for otp or reset password token

customise_devise.rb

module CustomiseDevise
  extend ActiveSupport::Concern

  included do
    attr_accessor :project_name, :mailer_host_name, :confirmation_required, :confirmation_type
    after_create :send_confirmation_instructions, if: :confirmation_required?

    class_eval do
      def confirmation_required?
        !!confirmation_required
      end

      def friendly_token(length = 20)
        return rand(10 ** 3...10 ** 4) if confirmation_type == 'OTP'
        rlength = (length * 3) / 4
        SecureRandom.urlsafe_base64(rlength).tr('lIO0', 'sxyz')
      end

      def generate_token
        token = self.friendly_token
        while User.where(confirmation_token: token).first
          token = self.friendly_token
        end
        token
      end

      # Generates a new random token for confirmation, and stores
      # the time this token is being generated in confirmation_sent_at
      def generate_confirmation_token
        if self.confirmation_token && !confirmation_period_expired?
          @raw_confirmation_token = self.confirmation_token
        else
          self.confirmation_token = @raw_confirmation_token = generate_token
          self.confirmation_sent_at = Time.now.utc
        end
      end
    end

    # override the devise method to set the mailer_host_name name
    class << self
      # set some project specific values here
      def set_project_specific_values resource, attributes = {}
        attributes[:mailer_host_name] || raise('Mailer host name not defined.')
        [:project_name, :mailer_host_name, :confirmation_type, :confirmation_required].each do |key|
          resource.send("#{key}=", attributes[key])
        end
      end

      def send_confirmation_instructions(attributes={})
        confirmable = find_by_unconfirmed_email_with_errors(attributes) if reconfirmable
        unless confirmable.try(:persisted?)
          confirmable = find_or_initialize_with_errors(confirmation_keys, attributes, :not_found)
        end
        set_project_specific_values(confirmable, attributes)
        confirmable.resend_confirmation_instructions if confirmable.persisted?
        confirmable
      end

      def send_reset_password_instructions(attributes={})
        recoverable = find_or_initialize_with_errors(reset_password_keys, attributes, :not_found)
        recoverable.send_reset_password_instructions if recoverable.persisted?
        set_project_specific_values(recoverable, attributes)
        recoverable
      end
    end
  end
end