webserver/proxy: Allow overriding proxy_http_version

This is needed for WebSocket

webserver/templates/locations/proxy.conf

@@ -35,6 +35,9 @@
         proxy_cookie_path / "/; Secure; HttpOnly; SameSite=Lax";
         {% endif %}
         {% endif %}
+        {% if location.proxy_http_version is defined %}
+        proxy_http_version {{location.proxy_http_version}};
+        {% endif %}
         {% if location.proxy_headers is defined %}
 
         {% for key, value in location.proxy_headers.items() %}