portainer: add nginx conf

roles/portainer/templates/portainer.conf.j2

@@ -0,0 +1,20 @@
+server {
+    listen 80;
+    server_name portainer.{{ base_domain }};
+    return 301 https://$host$request_uri;
+}
+
+server {
+    server_name portainer.{{ base_domain }};
+    listen 443 ssl http2;
+
+    include /etc/nginx/snippets/authelia-endpoint.conf;
+
+    location / {
+        include /etc/nginx/snippets/proxy.conf;
+        include /etc/nginx/snippets/authelia-auth.conf;
+
+        set $upstream http://portainer:9000; # This example assumes a Docker deployment
+        proxy_pass $upstream;
+    }
+}