Implement update

[khiav223577]

update

Updates the attributes of the model from the passed-in hash and saves the record. The difference between this method and ActiveRecord#update is that it will add extra WHERE conditions to prevent race condition.

Example:

class Arena < ApplicationRecord
  def atomically_close!
    atomically.update(closed_at: Time.now)
  end

  def close!
    update(closed_at: Time.now)
  end
end

# arena.atomically_close!
UPDATE `arenas` SET `arenas`.`closed_at` = '2018-11-27 03:44:25', `updated_at` = '2018-11-27 03:44:25' 
WHERE `arenas`.`id` = 1752 AND `arenas`.`closed_at` IS NULL

# arena.close!
UPDATE `arenas` SET `arenas`.`closed_at` = '2018-11-27 03:44:25', `updated_at` = '2018-11-27 03:44:25' 
WHERE `arenas`.`id` = 1752