Created new env var to programatically provide an initial API key

module/Rest/src/ApiKey/Repository/ApiKeyRepositoryInterface.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Rest\ApiKey\Repository;
+
+use Doctrine\Persistence\ObjectRepository;
+use Happyr\DoctrineSpecification\Repository\EntitySpecificationRepositoryInterface;
+
+interface ApiKeyRepositoryInterface extends ObjectRepository, EntitySpecificationRepositoryInterface
+{
+    /**
+     * Will create provided API key only if there's no API keys yet
+     */
+    public function createInitialApiKey(string $apiKey): void;
+}