良い実装か？は置いていて、controllerのconcernsをmodelから利用するやつ

app／controllers／concerns／slack_helper.rb

module SlackHelper
  extend ActiveSupport::Concern

  # メッセージを通知します
  def self.send_to_slack(message, channel:, mentions: nil, icon: ':fukurouchan:')
    mentions_line = SlackHelper.create_mentions_line(mentions)
    SlackHelper.send_core(mentions_line + message, channel, icon_emoji: icon)
  end
  delegate :send_to_slack, to: SlackHelper

app／models／hoge.rb

class Hoge < ApplicationRecord
  def foobar
    SlackHelper.send_to_slack('test model', channel: 'infra')
  end
end