website/docs: add nginx-proxy-manager

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/docs/providers/proxy/_nginx_standalone.md

@@ -0,0 +1,60 @@
+
+```
+server {
+    # SSL and VHost configuration
+    listen                  443 ssl http2;
+    server_name             _;
+
+    ssl_certificate         /etc/ssl/certs/ssl-cert-snakeoil.pem;
+    ssl_certificate_key     /etc/ssl/private/ssl-cert-snakeoil.key;
+
+    # Increase buffer size for large headers
+    # This is needed only if you get 'upstream sent too big header while reading response header from upstream' error when trying to access an application protected by goauthentik
+    proxy_buffers 8 16k;
+    proxy_buffer_size 32k;
+    fastcgi_buffers 16 16k;
+    fastcgi_buffer_size 32k;
+
+    location / {
+        # Put your proxy_pass to your application here
+        # proxy_pass          http://localhost:5000;
+
+        # authentik-specific config
+        auth_request        /akprox/auth/nginx;
+        error_page          401 = @akprox_signin;
+        # For domain level, use the below error_page to redirect to your authentik server with the full redirect path
+        # error_page          401 =302 https://authentik.company/akprox/start?rd=$scheme://$http_host$request_uri;
+
+        # translate headers from the outposts back to the actual upstream
+        auth_request_set $authentik_username $upstream_http_x_authentik_username;
+        auth_request_set $authentik_groups $upstream_http_x_authentik_groups;
+        auth_request_set $authentik_email $upstream_http_x_authentik_email;
+        auth_request_set $authentik_name $upstream_http_x_authentik_name;
+        auth_request_set $authentik_uid $upstream_http_x_authentik_uid;
+
+        proxy_set_header X-authentik-username $authentik_username;
+        proxy_set_header X-authentik-groups $authentik_groups;
+        proxy_set_header X-authentik-email $authentik_email;
+        proxy_set_header X-authentik-name $authentik_name;
+        proxy_set_header X-authentik-uid $authentik_uid;
+    }
+
+    # all requests to /akprox must be accessible without authentication
+    location /akprox {
+        proxy_pass          http://*ip or hostname of the authentik OUTPOST*:9000/akprox;
+        # ensure the host of this vserver matches your external URL you've configured
+        # in authentik
+        proxy_set_header    Host $host;
+        add_header          Set-Cookie $auth_cookie;
+        auth_request_set    $auth_cookie $upstream_http_set_cookie;
+    }
+
+    # Special location for when the /auth endpoint returns a 401,
+    # redirect to the /start URL which initiates SSO
+    location @akprox_signin {
+        internal;
+        add_header Set-Cookie $auth_cookie;
+        return 302 /akprox/start?rd=$request_uri;
+    }
+}
+```