```ruby
class AuditCertificate < ActiveRecord::Base
  include ShortlistedDocument
  include Reviewable

  begin :validations
    validates :attachment, presence: true,
                           on: :create,
                           file_size: {
                             maximum: 10.megabytes.to_i
                           }

    validates :form_answer_id, uniqueness: true,
              presence: true
  end

  before_save :clean_changes_description

  enum status: {
    no_changes_necessary: 0,
    confirmed_changes: 1
  }

  private

  def clean_changes_description
    if status_changed? && status == "no_changes_necessary" && changes_description.present?
      self.changes_description = nil
    end
  end
end
```

Increase upload file size for audit certificates
user
```ruby
class AuditCertificate < ActiveRecord::Base
  include ShortlistedDocument
  include Reviewable

  begin :validations
    validates :attachment, presence: true,
                           on: :create,
                           file_size: {
                             maximum: 15.megabytes.to_i
                           }

    validates :form_answer_id, uniqueness: true,
              presence: true
  end

  before_save :clean_changes_description

  enum status: {
    no_changes_necessary: 0,
    confirmed_changes: 1
  }

  private

  def clean_changes_description
    if status_changed? && status == "no_changes_necessary" && changes_description.present?
      self.changes_description = nil
    end
  end
end
```
assistant