normalize config file name for download to make it work on Windows

Windows client name is derived from config file name when importing to WireGuard and it only accepts names satisfying /^[a-zA-Z0-9_=+.-]{1,32}$/.
For more information look at af60ab2299/conf/name.go (L24).

src/lib/Server.js

@@ -99,7 +99,8 @@ module.exports = class Server {
         const { clientId } = req.params;
         const client = await WireGuard.getClient({ clientId });
         const config = await WireGuard.getClientConfiguration({ clientId });
-        res.header('Content-Disposition', `attachment; filename="${client.name}.conf"`);
+        const configName = client.name.replace(/[^a-zA-Z0-9_=+.-]/g, '-').replace(/(-{2,}|-$)/g, '-').replace(/-$/, '').substring(0, 32);
+        res.header('Content-Disposition', `attachment; filename="${configName}.conf"`);
         res.header('Content-Type', 'text/plain');
         res.send(config);
       }))