CREATE TABLE IF NOT EXISTS `messages` (
  `id` INT AUTO_INCREMENT PRIMARY KEY,
  `sender_id` INT NOT NULL,
  `recipient_id` INT NOT NULL,
  `content` TEXT NOT NULL,
  `is_read` BOOLEAN NOT NULL DEFAULT FALSE,
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (`sender_id`) REFERENCES `users`(`id`),
  FOREIGN KEY (`recipient_id`) REFERENCES `users`(`id`)
);