Created command to generate a random secret key string

module/CLI/config/cli.config.php

@@ -11,6 +11,7 @@ return [
             Command\GetVisitsCommand::class,
             Command\ProcessVisitsCommand::class,
             Command\Config\GenerateCharsetCommand::class,
+            Command\Config\GenerateSecretCommand::class,
             Command\Api\GenerateKeyCommand::class,
             Command\Api\DisableKeyCommand::class,
             Command\Api\ListKeysCommand::class,

module/CLI/config/dependencies.config.php

@@ -17,6 +17,7 @@ return [
             Command\ProcessVisitsCommand::class => AnnotatedFactory::class,
             Command\ProcessVisitsCommand::class => AnnotatedFactory::class,
             Command\Config\GenerateCharsetCommand::class => AnnotatedFactory::class,
+            Command\Config\GenerateSecretCommand::class => AnnotatedFactory::class,
             Command\Api\GenerateKeyCommand::class => AnnotatedFactory::class,
             Command\Api\DisableKeyCommand::class => AnnotatedFactory::class,
             Command\Api\ListKeysCommand::class => AnnotatedFactory::class,

module/CLI/src/Command/Config/GenerateSecretCommand.php

@@ -0,0 +1,45 @@
+<?php
+namespace Shlinkio\Shlink\CLI\Command\Config;
+
+use Acelaya\ZsmAnnotatedServices\Annotation\Inject;
+use Shlinkio\Shlink\Common\Util\StringUtilsTrait;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Zend\I18n\Translator\TranslatorInterface;
+
+class GenerateSecretCommand extends Command
+{
+    use StringUtilsTrait;
+
+    /**
+     * @var TranslatorInterface
+     */
+    private $translator;
+
+    /**
+     * GenerateCharsetCommand constructor.
+     * @param TranslatorInterface $translator
+     *
+     * @Inject({"translator"})
+     */
+    public function __construct(TranslatorInterface $translator)
+    {
+        $this->translator = $translator;
+        parent::__construct(null);
+    }
+
+    public function configure()
+    {
+        $this->setName('config:generate-secret')
+             ->setDescription($this->translator->translate(
+                 'Generates a random secret string that can be used for JWT token encryption'
+             ));
+    }
+
+    public function execute(InputInterface $input, OutputInterface $output)
+    {
+        $secret = $this->generateRandomString(32);
+        $output->writeln($this->translator->translate('Secret key:') . sprintf(' <info>%s</info>', $secret));
+    }
+}