Refactor authorization and token refresh logic; update tax handling and invoice generation

- Changed variable name from `$stmt_service` to `$stmt_refreshkey` for clarity in `authorization.php` and `token_refresh.php`.
- Added null coalescing operator to ensure criteria are set to an empty string if not provided in `products_software_versions.php`.
- Modified SQL script to add `eu` column to `taxes` table and update tax rates based on EU membership.
- Enhanced invoice generation logic in `functions.php` to include VAT notes based on customer country and VAT number.
- Updated email and PDF templates to display VAT notes and percentages correctly.
- Adjusted JavaScript tax calculation logic to handle VAT based on country and VAT number.
- Fixed API URL in `index.php` for token refresh endpoint.
- Updated countries data structure in `countries.php` to include EU membership status.

api/v2/get/products_software_versions.php

@@ -26,7 +26,7 @@ if(isset($get_content) && $get_content!=''){
     foreach ($requests as $y){
         $v = explode("=", $y);
         //INCLUDE VARIABLES IN ARRAY
-        $criterias[$v[0]] = $v[1]; 
+        $criterias[$v[0]] = $v[1] ?? ''; 
     
         if ($v[0] == 'page' || $v[0] =='p' || $v[0] =='totals' || $v[0] =='list' || $v[0] =='history'|| $v[0] =='success_msg'){
         //do nothing

api/v2/get/token_refresh.php

@@ -65,8 +65,8 @@ if ($stmt->rowCount() == 1) {
     //Refresh REFRESHKEY
     $user_data['refreshkey'] = bin2hex(random_bytes(25));
     $sql_refreshkey = 'UPDATE users SET refreshkey = ? WHERE id = ?';
-    $stmt_service = $pdo->prepare($sql_refreshkey);
-    $stmt_service->execute([$user_data['refreshkey'], $user_data['id']]);
+    $stmt_refreshkey = $pdo->prepare($sql_refreshkey);
+    $stmt_refreshkey->execute([$user_data['refreshkey'], $user_data['id']]);
 
     $token = createCommunicationToken($user_data['userkey']);