CREATE TABLE IF NOT EXISTS notifications (
  id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  sender_id INT UNSIGNED NOT NULL,
  title VARCHAR(255) NOT NULL,
  body TEXT NOT NULL,
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (sender_id) REFERENCES users(id) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

CREATE TABLE IF NOT EXISTS notification_recipients (
  notification_id INT UNSIGNED NOT NULL,
  user_id INT UNSIGNED NOT NULL,
  read_at DATETIME DEFAULT NULL,
  PRIMARY KEY (notification_id, user_id),
  FOREIGN KEY (notification_id) REFERENCES notifications(id) ON DELETE CASCADE,
  FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;