zammad/db/migrate/20200205000001_chat_add_allow_website.rb

class ChatAddAllowWebsite < ActiveRecord::Migration[5.1]
  def up

    # return if it's a new setup
    return if !Setting.find_by(name: 'system_init_done')

    add_column :chats, :whitelisted_websites, :string, limit: 5000, null: true
  end
end