add admin section to select groups allowed to print

lib/Config.php

@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\Printer;
+
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\IConfig;
+use OCP\IGroupManager;
+use OCP\IUser;
+use OCP\Security\ISecureRandom;
+
+class Config
+{
+    /**
+     * @var IConfig
+     */
+    protected $config;
+
+    /**
+     * @var ITimeFactory
+     */
+    protected $timeFactory;
+
+    /**
+     * @var IGroupManager
+     */
+    private $groupManager;
+
+    /**
+     * @var ISecureRandom
+     */
+    private $secureRandom;
+
+    public function __construct(IConfig $config, ISecureRandom $secureRandom, IGroupManager $groupManager, ITimeFactory $timeFactory)
+    {
+        $this->config = $config;
+        $this->secureRandom = $secureRandom;
+        $this->groupManager = $groupManager;
+        $this->timeFactory = $timeFactory;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getAllowedGroupIds(): array
+    {
+        $groups = $this->config->getAppValue('printer', 'allowed_groups', '[]');
+        $groups = json_decode($groups, true);
+
+        return \is_array($groups) ? $groups : [];
+    }
+
+    public function isDisabledForUser(IUser $user): bool
+    {
+        $allowedGroups = $this->getAllowedGroupIds();
+
+        if (empty($allowedGroups)) {
+            return false;
+        }
+
+        $userGroups = $this->groupManager->getUserGroupIds($user);
+
+        return empty(array_intersect($allowedGroups, $userGroups));
+    }
+}