fix cors issue with api

src/controllers/API.php

@@ -26,12 +26,49 @@ public function __construct()
         // Set the Content-Type header to application/json
         header("Content-Type:application/json");
 
-        // Allow access from any origin (CORS)
-        header('Access-Control-Allow-Origin: *');
+        // Allow access from any origin to avoid CORS issues
+        $this->cors();
 
         $this->resource = Utility::splitURL()[2] ?? "";
     }
 
+    /**
+     *  An example CORS-compliant method.  It will allow any GET, POST, or OPTIONS requests from any
+     *  origin.
+     *
+     *  In a production environment, you probably want to be more restrictive, but this gives you
+     *  the general idea of what is involved.  For the nitty-gritty low-down, read:
+     *
+     *  - https://developer.mozilla.org/en/HTTP_access_control
+     *  - https://fetch.spec.whatwg.org/#http-cors-protocol
+     *    Reference: https://stackoverflow.com/a/9866124/17627866
+     */
+    private function cors(): void
+    {
+        // Allow from any origin
+        if (isset($_SERVER['HTTP_ORIGIN'])) {
+            // Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
+            // you want to allow, and if so:
+            header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
+            header('Access-Control-Allow-Credentials: true');
+            header('Access-Control-Max-Age: 86400');    // cache for 1 day
+        }
+
+        // Access-Control headers are received during OPTIONS requests
+        if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
+            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD'])) // may also be using PUT, PATCH, HEAD etc
+            {
+                header("Access-Control-Allow-Methods: GET, POST, OPTIONS");
+            }
+
+            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])) {
+                header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
+            }
+
+            exit(0);
+        }
+    }
+
     /**
      * Checks if root relative url starts with api/v1
      * @return bool