{
  _id: new MongoId(),
  type: int,
  order_number: int,
  doc: {
    _id: MongoId
  },
  sender: {
    user_id: id,
    folder_id: int,
    dates: {
      added: timestamp with timezone,
      sent: timestamp with timezone,
      deleted: timestamp with timezone
    },
    send_copy: bool
  },
  recipient: {
    user_id: int,
    office_id: int,
    bussines_id: int,
    folder_id: int,
    dates: {
      read: timestamp with timezone,
      deleted: timestamp with timezone
    },
    include_protocol: bool
  },
  is_self_note : string,
  subject : string,
  content : text,
  attachments {        // прикрепленные файлы
    {
      binary_file: MongoBinary,
      filename: string,
      deleted: bool
    }
  }
}