Improve routing between containers

Create user network nginx-internal
and use Docker's internal DNS server
to resolve containers by hostname.

roles/jellyfin/tasks/main.yml

@@ -11,6 +11,8 @@
   docker_container:
     name: 'jellyfin'
     image: linuxserver/jellyfin
+    networks:
+      - name: nginx-internal
     volumes:
       - "{{ data_folder }}/jellyfin:/config"
       - "{{ media.tv }}:/data/tv"