Update example nginx config

To account for our subdomain recommendations

docs/docs/configuration/cheatsheet.md

@@ -396,7 +396,8 @@ This section describe PWA manifest instance-specific values. Currently this opti
 ## :media_proxy
 
 * `enabled`: Enables proxying of remote media to the instance’s proxy
-* `base_url`: The base URL to access a user-uploaded file. Useful when you want to proxy the media files via another host/CDN fronts.
+* `base_url`: The base URL to access a user-uploaded file.
+  Using a (sub)domain distinct from the instance endpoint is **strongly** recommended.
 * `proxy_opts`: All options defined in `Pleroma.ReverseProxy` documentation, defaults to `[max_body_length: (25*1_048_576)]`.
 * `whitelist`: List of hosts with scheme to bypass the mediaproxy (e.g. `https://example.com`)
 * `invalidation`: options for remove media from cache after delete object:

installation/nginx/akkoma.nginx

@@ -75,9 +75,48 @@ server {
     proxy_set_header Host $http_host;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 
+    location ~ ^/(media|proxy) {
+        return 404;
+    }
+
     location / {
         proxy_pass http://phoenix;
     }
+}
+
+# Upload and MediaProxy Subdomain
+# (see main domain setup for more details)
+server {
+    server_name    media.example.tld;
+
+    listen         80;
+    listen         [::]:80;
+
+    location / {
+      return         301 https://$server_name$request_uri;
+    }
+}
+
+server {
+    server_name media.example.tld;
+
+    listen 443 ssl http2;
+    listen [::]:443 ssl http2;
+
+    ssl_trusted_certificate   /etc/letsencrypt/live/media.example.tld/chain.pem;
+    ssl_certificate           /etc/letsencrypt/live/media.example.tld/fullchain.pem;
+    ssl_certificate_key       /etc/letsencrypt/live/media.example.tld/privkey.pem;
+    # .. copy all other the ssl_* and gzip_* stuff from main domain
+
+    # the nginx default is 1m, not enough for large media uploads
+    client_max_body_size 16m;
+    ignore_invalid_headers off;
+
+    proxy_http_version 1.1;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection "upgrade";
+    proxy_set_header Host $http_host;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 
     location ~ ^/(media|proxy) {
         proxy_cache        akkoma_media_cache;
@@ -91,4 +130,8 @@ server {
         chunked_transfer_encoding on;
         proxy_pass         http://phoenix;
     }
+
+    location / {
+        return 404;
+    }
 }