make it possible to have username

src/Cli/AddUserCommand.php

@@ -21,6 +21,11 @@ class AddUserCommand extends Command
 
     public function execute(InputInterface $input, OutputInterface $output): int
     {
+        if (!filter_var($input->getArgument('email'), FILTER_VALIDATE_EMAIL)) {
+            $output->writeln('<error>Please provide a valid email address.</error>');
+            return 1;
+        }
+
         $user = new User();
         $user->setEmail($input->getArgument('email'));
         $user->setPlainPassword($input->getArgument('password'));