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/ca-bundle/composer.json

@@ -0,0 +1,54 @@
+{
+    "name": "composer\/ca-bundle",
+    "description": "Lets you find a path to the system CA bundle, and includes a fallback to the Mozilla CA bundle.",
+    "type": "library",
+    "license": "MIT",
+    "keywords": [
+        "cabundle",
+        "cacert",
+        "certificate",
+        "ssl",
+        "tls"
+    ],
+    "authors": [
+        {
+            "name": "Jordi Boggiano",
+            "email": "j.boggiano@seld.be",
+            "homepage": "http:\/\/seld.be"
+        }
+    ],
+    "support": {
+        "irc": "irc:\/\/irc.freenode.org\/composer",
+        "issues": "https:\/\/github.com\/composer\/ca-bundle\/issues"
+    },
+    "require": {
+        "ext-openssl": "*",
+        "ext-pcre": "*",
+        "php": "^5.3.2 || ^7.0 || ^8.0"
+    },
+    "require-dev": {
+        "symfony\/phpunit-bridge": "^4.2 || ^5",
+        "phpstan\/phpstan": "^0.12.55",
+        "psr\/log": "^1.0",
+        "symfony\/process": "^2.5 || ^3.0 || ^4.0 || ^5.0 || ^6.0"
+    },
+    "autoload": {
+        "psr-4": {
+            "_PhpScoperf7c63b60b99d\\Composer\\CaBundle\\": "src"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "_PhpScoperf7c63b60b99d\\Composer\\CaBundle\\": "tests"
+        }
+    },
+    "extra": {
+        "branch-alias": {
+            "dev-main": "1.x-dev"
+        }
+    },
+    "scripts": {
+        "test": "SYMFONY_PHPUNIT_REMOVE_RETURN_TYPEHINT=1 vendor\/bin\/simple-phpunit",
+        "phpstan": "vendor\/bin\/phpstan analyse"
+    }
+}