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/CustomerEndpoint.php

@@ -0,0 +1,111 @@
+<?php
+
+namespace Mollie\Api\Endpoints;
+
+use Mollie\Api\Exceptions\ApiException;
+use Mollie\Api\Resources\Customer;
+use Mollie\Api\Resources\CustomerCollection;
+class CustomerEndpoint extends \Mollie\Api\Endpoints\CollectionEndpointAbstract
+{
+    protected $resourcePath = "customers";
+    /**
+     * @var string
+     */
+    public const RESOURCE_ID_PREFIX = 'cst_';
+    /**
+     * Get the object that is used by this API endpoint. Every API endpoint uses one type of object.
+     *
+     * @return Customer
+     */
+    protected function getResourceObject()
+    {
+        return new \Mollie\Api\Resources\Customer($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 $_links
+     *
+     * @return CustomerCollection
+     */
+    protected function getResourceCollectionObject($count, $_links)
+    {
+        return new \Mollie\Api\Resources\CustomerCollection($this->client, $count, $_links);
+    }
+    /**
+     * Creates a customer in Mollie.
+     *
+     * @param array $data An array containing details on the customer.
+     * @param array $filters
+     *
+     * @return Customer
+     * @throws ApiException
+     */
+    public function create(array $data = [], array $filters = [])
+    {
+        return $this->rest_create($data, $filters);
+    }
+    /**
+     * Retrieve a single customer from Mollie.
+     *
+     * Will throw a ApiException if the customer id is invalid or the resource cannot be found.
+     *
+     * @param string $customerId
+     * @param array $parameters
+     * @return Customer
+     * @throws ApiException
+     */
+    public function get($customerId, array $parameters = [])
+    {
+        return $this->rest_read($customerId, $parameters);
+    }
+    /**
+     * Update a specific Customer resource.
+     *
+     * Will throw an ApiException if the customer id is invalid or the resource cannot be found.
+     *
+     * @param string $customerId
+     *
+     * @param array $data
+     * @return Customer
+     * @throws ApiException
+     */
+    public function update($customerId, array $data = [])
+    {
+        if (empty($customerId) || \strpos($customerId, self::RESOURCE_ID_PREFIX) !== 0) {
+            throw new \Mollie\Api\Exceptions\ApiException("Invalid order ID: '{$customerId}'. An order ID should start with '" . self::RESOURCE_ID_PREFIX . "'.");
+        }
+        return parent::rest_update($customerId, $data);
+    }
+    /**
+     * Deletes the given Customer.
+     *
+     * Will throw a ApiException if the customer id is invalid or the resource cannot be found.
+     * Returns with HTTP status No Content (204) if successful.
+     *
+     * @param string $customerId
+     *
+     * @param array $data
+     * @return null
+     * @throws ApiException
+     */
+    public function delete($customerId, array $data = [])
+    {
+        return $this->rest_delete($customerId, $data);
+    }
+    /**
+     * Retrieves a collection of Customers from Mollie.
+     *
+     * @param string $from The first customer ID you want to include in your list.
+     * @param int $limit
+     * @param array $parameters
+     *
+     * @return CustomerCollection
+     * @throws ApiException
+     */
+    public function page($from = null, $limit = null, array $parameters = [])
+    {
+        return $this->rest_list($from, $limit, $parameters);
+    }
+}