We cat the options file, append the proxy image and then pass it
to xargs to ensure it handles spaces correctly.
Works better than using eval which can handle spaces but tries
to evaluate things like backticks.
Fixes: https://github.com/basecamp/kamal/issues/1448
Use localhost for app_with_roles and 127.0.0.1 for app. Confirm we can
deploy both and the respond to requests. Ensure the proxy is removed
once both have been removed.
1. Update to kamal-proxy 0.4.0 which creates and chowns
/home/kamal-proxy/.config/kamal-proxy to kamal-proxy
2. Use a docker volume rather than mapping in a directory, so docker
keeps it owned by the correct user
The proxy can be enabled via the config:
```
proxy:
enabled: true
hosts:
- 10.0.0.1
- 10.0.0.2
```
This will enable the proxy and cause it to be run on the hosts listed
under `hosts`, after running `kamal proxy reboot`.
Enabling the proxy disables `kamal traefik` commands and replaces them
with `kamal proxy` ones. However only the marked hosts will run the
kamal-proxy container, the rest will run Traefik as before.
