URL encode variables that go into a MySQL credentials URI

See for reference:
- https://dev.mysql.com/doc/refman/8.0/en/connecting-using-uri-or-key-value-pairs.html#connecting-using-uri
- https://symfony.com/doc/current/doctrine.html
but note that we must use `rawurlencode` instead of `urlencode` which
differ in how they encode a space (as tested).

Fixes: DOMjudge#2651
Closes: DOMjudge#2502 as this is likely fixed but I couldn't reproduce it

webapp/config/load_db_secrets.php

@@ -36,7 +36,11 @@ function get_db_url(): string
         break;
     }
 
-    return sprintf('mysql://%s:%s@%s:%d/%s?serverVersion=5.7.0', $user, $pass, $host, $port ?? 3306, $db);
+    return sprintf(
+        'mysql://%s:%s@%s:%d/%s?serverVersion=5.7.0',
+        rawurlencode($user), rawurlencode($pass), rawurlencode($host),
+        $port ?? 3306, rawurlencode($db)
+    );
 }
 
 function get_app_secret(): string

webapp/config/packages/doctrine.yaml

@@ -7,7 +7,7 @@ doctrine:
             charset: utf8mb4
             collate: utf8mb4_unicode_ci
 
-        url: '%env(resolve:DATABASE_URL)%'
+        url: '%env(DATABASE_URL)%'
         profiling_collect_backtrace: '%kernel.debug%'
         types:
             tinyint: App\Doctrine\DBAL\Types\TinyIntType