Use the --registry, --repository and --image_version options of
`kamal proxy boot_config set` to change the kamal-proxy image used.
We'll still insist that the image version is at least as high as the
minimum.
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
Add commands for managing proxy boot config. Since the proxy can be
shared by multiple applications, the configuration doesn't belong in
`config/deploy.yml`.
Instead you can set the config with:
```
Usage:
kamal proxy boot_config <set|get|clear>
Options:
[--publish], [--no-publish], [--skip-publish] # Publish the proxy ports on the host
# Default: true
[--http-port=N] # HTTP port to publish on the host
# Default: 80
[--https-port=N] # HTTPS port to publish on the host
# Default: 443
[--docker-options=option=value option2=value2] # Docker options to pass to the proxy container
```
By default we boot the proxy with `--publish 80:80 --publish 443:443`.
You can stop it from publishing ports, specify different ports and pass
other docker options.
The config is stored in `.kamal/proxy/options` as arguments to be passed
verbatim to docker run.
Where someone wants to set the options in their application they can do
that by calling `kamal proxy boot_config set` in a pre-deploy hook.
There's an example in the integration tests showing how to use this to
front kamal-proxy with Traefik, using an accessory.
