Add guest endpoint for validating customer number existence

- Introduced `POST /guest/validation/customer-number` in `guestRoute` to validate customer number existence.
- Implemented checks for required parameter format and range.
- Integrated `users_o` to verify if the customer number exists.

services/nginx/app/routes/guestRoute.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace routes;
+
+use classes\authentication;
+use classes\recaptcha;
+use objects\logs_o;
+use objects\tokens_o;
+use objects\users_o;
+use traits\route_t;
+
+class guestRoute
+{
+    use route_t;
+
+    public function run(): void
+    {
+        $this->post('/guest/validation/customer-number', function () {
+            // Get the post data
+            global $response;
+            self::requireParameters(['customer_number']);
+            // Validate the customer number
+            $customer_number = (int)$this->getParameter('customer_number');
+            self::requireType($customer_number, $this->type_int());
+            self::requireMinValue($customer_number, 1);
+            self::requireMaxValue($customer_number, 999999999);
+            $customer_number = (int)$this->getParameter('customer_number');
+            // Check if the customer number exists
+            $doesCustomerExist = (new users_o())->getUserByCustomerNumber($customer_number)->exists();
+
+            // Return the result
+            $response->success(['exists' => $doesCustomerExist, 'customer_number' => $customer_number]);
+        });
+    }
+}