feat: proxying support

Part of https://git.coopcloud.tech/coop-cloud/matrix-synapse/issues/1.

nginx.conf.tmpl

@@ -0,0 +1,26 @@
+user www-data;
+
+events {
+  worker_connections 768;
+}
+
+http {
+  upstream backend {
+    server {{ env "STACK_NAME" }}_app:8008;
+  }
+
+  include /etc/nginx/mime.types;
+
+  server {
+    listen 80;
+    server_name {{ env "DOMAIN" }};
+
+    location ~* ^(\/_matrix|\/_synapse\/client) {
+      proxy_pass http://backend;
+      proxy_set_header X-Forwarded-For $remote_addr;
+      proxy_set_header X-Forwarded-Proto $scheme;
+      proxy_set_header Host $host;
+      client_max_body_size 50M;
+    }
+  }
+}