fix: resolve container backends dynamically to allow nginx startup

conf.d/20-defaults.conf.template

@@ -0,0 +1,27 @@
+http2 on;
+ssl_protocols TLSv1.2 TLSv1.3;
+ssl_session_cache shared:SSL:10m;
+ssl_session_timeout 10m;
+ssl_session_tickets off;
+
+# OCSP stapling requires certificates with an OCSP responder URL.
+# Uncomment when the origin certificate supports it.
+# ssl_stapling on;
+# ssl_stapling_verify on;
+# resolver 1.1.1.1 8.8.8.8 valid=300s;
+# resolver_timeout 5s;
+
+server {
+    listen 80 default_server;
+    listen [::]:80 default_server;
+    server_name _;
+
+    return 301 https://$host$request_uri;
+}
+
+server {
+    listen 443 ssl default_server;
+    listen [::]:443 ssl default_server;
+
+    ssl_reject_handshake on;
+}