Updated logic to generate random short codes, increasing entropy

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

@@ -5,7 +5,6 @@ declare(strict_types=1);
 namespace Shlinkio\Shlink\CLI\Command\Config;
 
 use Shlinkio\Shlink\CLI\Util\ExitCodes;
-use Shlinkio\Shlink\Core\Options\UrlShortenerOptions;
 use Symfony\Component\Console\Command\Command;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
@@ -18,6 +17,7 @@ use function str_shuffle;
 class GenerateCharsetCommand extends Command
 {
     public const NAME = 'config:generate-charset';
+    private const DEFAULT_CHARS = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
 
     protected function configure(): void
     {
@@ -26,14 +26,14 @@ class GenerateCharsetCommand extends Command
             ->setDescription(sprintf(
                 '[DEPRECATED] Generates a character set sample just by shuffling the default one, "%s". '
                 . 'Then it can be set in the SHORTCODE_CHARS environment variable',
-                UrlShortenerOptions::DEFAULT_CHARS
+                self::DEFAULT_CHARS
             ))
             ->setHelp('<fg=red;options=bold>This command is deprecated. Better leave shlink generate the charset.</>');
     }
 
     protected function execute(InputInterface $input, OutputInterface $output): ?int
     {
-        $charSet = str_shuffle(UrlShortenerOptions::DEFAULT_CHARS);
+        $charSet = str_shuffle(self::DEFAULT_CHARS);
         (new SymfonyStyle($input, $output))->success(sprintf('Character set: "%s"', $charSet));
         return ExitCodes::EXIT_SUCCESS;
     }