Add ftl dev --background-after-deploy or alter existing --background to have this behaviour

[alecthomas]

This is typically what I want to do in shell scripts eg.

ftl dev --background-after-deploy .
trap "ftl dev --stop --no-serve" EXIT ERR SIGINT
ftl call foo.bar

[wesbillman]

It's an extra command, but we can use serve as well.

ftl serve --background
trap "ftl serve --stop" EXIT ERR SIGINT
ftl deploy .
ftl call foo.bar

[alecthomas]

We're getting rid of serves though IIRC

[stuartwdouglas]

I had a look at this, and it needs some way for the background process to signify that it is done deploying to the outer process that launched it. I don't think we want to open a socket or declare a new service just for this, so I am not really sure what the best approach is here. Maybe an extra field on the controller status to indicate that all initial dev deployments are done, but that also feels a bit yuck.