Created new Installer module and moved everything from CLI there

module/Installer/src/Config/Plugin/ApplicationConfigCustomizer.php

@@ -0,0 +1,44 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Installer\Config\Plugin;
+
+use Shlinkio\Shlink\Common\Util\StringUtilsTrait;
+use Shlinkio\Shlink\Installer\Model\CustomizableAppConfig;
+use Symfony\Component\Console\Style\SymfonyStyle;
+
+class ApplicationConfigCustomizer implements ConfigCustomizerInterface
+{
+    use StringUtilsTrait;
+
+    /**
+     * @param SymfonyStyle $io
+     * @param CustomizableAppConfig $appConfig
+     * @return void
+     */
+    public function process(SymfonyStyle $io, CustomizableAppConfig $appConfig)
+    {
+        $io->title('APPLICATION');
+
+        if ($appConfig->hasApp() && $io->confirm('Do you want to keep imported application config?')) {
+            return;
+        }
+
+        $validator = function ($value) {
+            return $value;
+        };
+        $appConfig->setApp([
+            'SECRET' => $io->ask(
+                'Define a secret string that will be used to sign API tokens (leave empty to autogenerate one)',
+                null,
+                $validator
+            ) ?: $this->generateRandomString(32),
+            'DISABLE_TRACK_PARAM' => $io->ask(
+                'Provide a parameter name that you will be able to use to disable tracking on specific request to '
+                . 'short URLs (leave empty and this feature won\'t be enabled)',
+                null,
+                $validator
+            ),
+        ]);
+    }
+}