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/src/Endpoints/ChargebackEndpoint.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Mollie\Api\Endpoints;
+
+use Mollie\Api\Exceptions\ApiException;
+use Mollie\Api\Resources\Chargeback;
+use Mollie\Api\Resources\ChargebackCollection;
+class ChargebackEndpoint extends \Mollie\Api\Endpoints\CollectionEndpointAbstract
+{
+    protected $resourcePath = "chargebacks";
+    /**
+     * Get the object that is used by this API endpoint. Every API endpoint uses one type of object.
+     *
+     * @return Chargeback
+     */
+    protected function getResourceObject()
+    {
+        return new \Mollie\Api\Resources\Chargeback($this->client);
+    }
+    /**
+     * Get the collection object that is used by this API endpoint. Every API endpoint uses one type of collection object.
+     *
+     * @param int $count
+     * @param \stdClass $_links
+     *
+     * @return ChargebackCollection
+     */
+    protected function getResourceCollectionObject($count, $_links)
+    {
+        return new \Mollie\Api\Resources\ChargebackCollection($this->client, $count, $_links);
+    }
+    /**
+     * Retrieves a collection of Chargebacks from Mollie.
+     *
+     * @param string $from The first chargeback ID you want to include in your list.
+     * @param int $limit
+     * @param array $parameters
+     *
+     * @return ChargebackCollection
+     * @throws ApiException
+     */
+    public function page($from = null, $limit = null, array $parameters = [])
+    {
+        return $this->rest_list($from, $limit, $parameters);
+    }
+}