Fix reverse proxy subpath support (#192)

docs/administration/nginx-reverse-proxy.md

@@ -1,6 +1,10 @@
 # Use Nginx as a reverse proxy
 
-Configure Nginx to proxy requests to Opengist. Here is an example configuration file :
+Configure Nginx to proxy requests to Opengist. Here are example configuration file to use Opengist on a subdomain or on a subpath.
+
+Make sure you set the base url for Opengist via the [configuration](/docs/configuration/cheat-sheet.md).
+
+### Subdomain
 ```
 server {
     listen 80;
@@ -16,7 +20,27 @@ server {
 }
 ```
 
-Then run :
-```shell
-service nginx restart
+### Subpath
+```
+server {
+    listen 80;
+    server_name example.com;
+
+    location /opengist/ {
+        rewrite ^/opengist(/.*)$ $1 break;
+        proxy_pass http://127.0.0.1:6157;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_set_header X-Forwarded-Prefix /opengist;
+    }
+}
+```
+
+---
+
+To apply changes:
+```shell
+sudo systemctl restart nginx
 ```