Add Mollie API integration and webhook for software upgrade payments

- Introduced the `CaBundle.php` class for managing CA certificates.
- Updated `installed.json` and `installed.php` to include the new `composer/ca-bundle` dependency.
- Added `platform_check.php` to enforce PHP version requirements.
- Created `initialize.php` for initializing the Mollie API client with the API key.
- Implemented `webhook_mollie.php` to handle webhook callbacks for software upgrade payments, including transaction status updates and invoice generation.
- Integrated DomPDF for generating invoices and sending them via email.

assets/mollie/vendor/composer/autoload_real.php

@@ -0,0 +1,39 @@
+<?php
+
+// autoload_real.php @generated by Composer
+
+class ComposerAutoloaderInit617dbc66d182e97844e7363117763c69
+{
+    private static $loader;
+
+    public static function loadClassLoader($class)
+    {
+        if ('Composer\Autoload\ClassLoader' === $class) {
+            require __DIR__ . '/ClassLoader.php';
+        }
+    }
+
+    /**
+     * @return \Composer\Autoload\ClassLoader
+     */
+    public static function getLoader()
+    {
+        if (null !== self::$loader) {
+            return self::$loader;
+        }
+
+        require __DIR__ . '/platform_check.php';
+
+        spl_autoload_register(array('ComposerAutoloaderInit617dbc66d182e97844e7363117763c69', 'loadClassLoader'), true, true);
+        self::$loader = $loader = new \Composer\Autoload\ClassLoader(\dirname(__DIR__));
+        spl_autoload_unregister(array('ComposerAutoloaderInit617dbc66d182e97844e7363117763c69', 'loadClassLoader'));
+
+        require __DIR__ . '/autoload_static.php';
+        call_user_func(\Composer\Autoload\ComposerStaticInit617dbc66d182e97844e7363117763c69::getInitializer($loader));
+
+        $loader->setClassMapAuthoritative(true);
+        $loader->register(true);
+
+        return $loader;
+    }
+}