lowercase login user

src/Repository/UserRepository.php

@@ -71,6 +71,8 @@ class UserRepository
 
     public function findByNick(string $nick): ?User
     {
+        $nick = strtolower(string: $nick);
+
         $sql = "
             SELECT id, nick, password, first, last, is_admin
             FROM " . DatabaseConnection::TABLE_USERS . "