class Contact
  attr_accessor :auth_token

  def initialize(contact_hash)
     ...
  end

  def edit(...)
     auth_token.can! :read, self
  end
end

token = AuthorizationToken.new(session)
contact = SomeService.get_contact(...)

contact.edit(...)
# raise error because auth_token is not set

contact.auth_token = token

contact.edit(...)

class QueryService
  def initialize(session)
    token = AuthorizationToken(session)
  end

  def get_contact
    contact = SomeService.get_contact(...)
    contact.token = token
  end
end

contact = QueryService.new(session).get_contact(...)
contact.edit(...)