Add support for background tasks

[beenje]

Problem description

I found 2 PRs attempting to add background tasks support: #386 and #682

Both were closed, as not complete and having problem supporting windows.

I'd really like this feature!
Opening this issue so it doesn't get forgotten and hoping someone will give it another try :-)

[ruben-arts]

Could you add a use-case and some more information why this is useful to you?

[ytausch]

I am also interested in this feature. My use case is: I want a jupyter task that runs jupyter in the background, and a ui task that starts our business UI (which also runs in the background). ui needs jupyter to be running, otherwise it will fail. With proper pixi integration, I would expect to be able to use depends_on for specifying that jupyter needs to be started before the UI can be run.

[wolfv]

For reference, the PR that @hadim made was really good and we could totally revive it.

[beenje]

To add my use case: I work a lot with tango-controls, which requires a Tango database to be running. For local development, I'd like to run pixi run tango-db to start Databaseds 2 -ORBendPoint giop:tcp:0.0.0.0:10000 in the background. It's then possible to register and run another tango server.