variable value comment
HTTP_HOST benev.laruelle.ch by default, NPM will use the defined hostname (mandatory for HTTPS SNI), but host may be overwritten by setting « $_host » variable
set $_host www.example.com;
REQUEST_URI /help/ request URI may be rewritten
rewrite /whatever/(.*) /help/$1 break;
response may also be rewritten
proxy_set_header Accept-Encoding "";
sub_filter '<a href="/help/' '<a href="/whatever/';
sub_filter_once off;
test (look at the URL by putting the mouse over): /help/
HTTP_CONNECTION
Warning: Undefined array key "HTTP_CONNECTION" in /var/www/html/help/index.php on line 46
 closed: HTTP 1.0
keep-alive: HTTP 1.1 (websocket)

websocket may be enabled globally for the site (NPM option),
or for a specific location: 
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
ACCEPT_ENCODING gzip, br, zstd, deflate disable compression for using sub_filter
proxy_set_header Accept-Encoding "";
HTTP_X_FORWARDED_SCHEME https
HTTP_X_FORWARDED_PROTO https
HTTP_X_FORWARDED_FOR 216.73.217.134
HTTP_X_REAL_IP 216.73.217.134