feat: add index file service interface

Author: jankal

src/Service/IndexFileServiceInterface.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace NuonicPluginInstaller\Service;
+
+use NuonicPluginInstaller\Struct\PackageIndexEntry;
+
+interface IndexFileServiceInterface
+{
+    public function getPackageInformation(string $packageName): PackageIndexEntry;
+
+    /**
+     * @return PackageIndexEntry[]
+     */
+    public function listPackages(): array;
+}

src/Struct/PackageIndexEntry.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace NuonicPluginInstaller\Struct;
+
+use Shopware\Core\Framework\Struct\Struct;
+
+class PackageIndexEntry extends Struct
+{
+    public function __construct(
+        public string $repositoryUrl,
+        public string $ref,
+    ) {
+    }
+}