Refactor API structure: update internal handling, enhance input retrieval, and improve template loading

api/auth/login.php

@@ -2,22 +2,16 @@
 // Set internal to false so that the answer goes to the client
 if (!isset($internal)) {
     $internal = false;
+    define("API_DIR", "../");
 }
 
 // Load API Library
-require "../api.php";
+require API_DIR . "api.php";
 
-$api = new gbAPI(false);
+$api = new gbAPI(false, $internal);
 
 // Check Request Body
-if ($_SERVER["REQUEST_METHOD"] !== "POST") {
-    $api->answer(400, [
-        "error" => "false_request_method",
-        "error_text" => "Only POST allowed"
-    ], true);
-}
-
-$input = json_decode(file_get_contents("php://input"), true);
+$input = $api->getInput();
 
 if (!isset($input["username"]) || !isset($input["password"])) {
     $api->answer(400, [