Nginx conf reverse proxy for Rails 5.2.1 Puma with SSL

nginx.conf

location @app {
  proxy_set_header X-Real-IP $remote_addr;
  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_set_header Host $http_host;
  proxy_redirect off;
  proxy_pass http://app_upstream;
  proxy_set_header Upgrade $http_upgrade;
  proxy_set_header Connection "upgrade";
      
  proxy_set_header X-Forwarded-Proto $scheme;
  proxy_set_header X-Forwarded-Ssl on; # Optional
  proxy_set_header X-Forwarded-Port $server_port;
  proxy_set_header X-Forwarded-Host $host;
}