/*
 * This file provides a helper function `sendNotification` to abstract notification logic.
 * It is intended to be included by other API endpoints.
 *
 * Function Signature:
 * sendNotification(int $user_id, string $title, string $message, string $level): bool
 *
 * Parameters:
 * - $user_id: The ID of the recipient user.
 * - $title: The title of the notification.
 * - $message: The body of the notification.
 * - $level: The notification level ('important', 'normal', 'low').
 *
 * Returns:
 * - true if the notification was successfully sent (inserted into DB), false otherwise.
 */

/*
 * Example of how another API endpoint would use this function:
 *
 * require_once __DIR__ . '/../../api/notifications/notify.php'; // Include this file
 *
 * $recipient_user_id = 123;
 * $notification_title = "Booking Approved!";
 * $notification_message = "Your booking for property XYZ has been approved by the host.";
 * $notification_level = "important";
 *
 * if (sendNotification($recipient_user_id, $notification_title, $notification_message, $notification_level)) {
 *     // Notification sent successfully
 * } else {
 *     // Log error or handle failure
 * }
 */

/*
 * Example Request JSON (if this file were an API endpoint directly):
 * {
 *   "user_id": 101,
 *   "title": "New Message Received",
 *   "message": "You have a new message from the host.",
 *   "level": "normal" // 'important', 'normal', or 'low'
 * }
 */

/*
 * Example Response JSON (if this file were an API endpoint directly - Success):
 * {
 *   "message": "Notification sent successfully."
 * }
 */

/*
 * Example Response JSON (if this file were an API endpoint directly - Error):
 * {
 *   "message": "Missing required fields: user_id, title, message, level."
 * }
 */