Devenv: Add serve_from_sub_path scenario to nginx devenv (#93691)

Setup serve_from_sub_path scenario with nginx

devenv/docker/blocks/auth/nginx_proxy/nginx_serve_from_sub_path.conf

@@ -0,0 +1,39 @@
+events { worker_connections 1024; }
+
+http {
+  # This is required to proxy Grafana Live WebSocket connections.
+  map $http_upgrade $connection_upgrade {
+    default upgrade;
+    '' close;
+  }
+
+  upstream grafana {
+    server host.docker.internal:3000;
+  }
+
+  server {
+    listen 8090;
+
+    location / {
+      root /var/www/html;
+    }
+
+    # Set the followings in grafana.ini:
+    # [server]
+    # root_url = http://localhost:8090/grafana/
+    # serve_from_sub_path = true
+    location /grafana/ {
+      proxy_set_header Host $host;
+      proxy_pass http://grafana;
+    }
+
+    # Proxy Grafana Live WebSocket connections.
+    location /grafana/api/live/ {
+      proxy_http_version 1.1;
+      proxy_set_header Upgrade $http_upgrade;
+      proxy_set_header Connection $connection_upgrade;
+      proxy_set_header Host $host;
+      proxy_pass http://grafana;
+    }
+  }
+}