Allow multiple apps to be deployed to the same server

[jaydrogers]

👉 Describe the problem

Spin only supports one app stack to be deployed to a server.

👥 Problem evidence & reach

• https://discord.com/channels/910287105714954251/910299290230997003/1316075190026895452

🥰 Describe the "impact" on users?

This could save some users money and complexity so they don't need to manage multiple servers.

🏆 How to solve this problem

Create a "Spin Proxy" variable

This could be something enabled in the .spin.yml where users could enable "multitenancy". This would have the Ansible playbook create a default proxy (like Traefik). Once that "global service" is running, then users can use external networks to join to the proxy: https://docs.docker.com/compose/how-tos/networking/#use-a-pre-existing-network

💯 How do we validate the problem is solved?

• A user can deploy multiple apps to the same server