426 Upgrade header MUST be provided
Salutations,

I have an issue to connect to my Ratchet Websocket server.
I got this error: `426 Upgrade header MUST be provided`
Any idea?

**Request Header**
```
HTTP/1.1 426 Upgrade header MUST be provided
Date: Wed, 03 Feb 2021 13:30:53 GMT
Server: Apache/2.4.41 (Ubuntu)
Sec-WebSocket-Version: 13
X-Powered-By: Ratchet/0.4.3
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/html
```

**Response Header**
```
GET / HTTP/1.1
Host: my-domain.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:85.0) Gecko/20100101 Firefox/85.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Connection: keep-alive
Upgrade-Insecure-Requests: 1
Pragma: no-cache
Cache-Control: no-cache
```
**Apache config**
```
<VirtualHost *:80>
    ServerName www.my-domain.com
    ServerAlias my-domain.com
    ServerAdmin example@gmail.com
    DocumentRoot /var/www/my-domain.com

    RewriteEngine on
    RewriteCond ${HTTP:Upgrade} websocket [NC]
    RewriteCond ${HTTP:Connection} upgrade [NC]
    RewriteRule .* "ws:/localhost:3000/$1" [P,L]

    ProxyPass / http://localhost:3000/
    ProxyPassReverse / http://localhost:3000/
    ProxyRequests off
</VirtualHost>
```