Draft remaining user stories for first milestone

I'm not quite sure what's the best way to express the desired features for the first milestone (%Basic network of package build daemons). I'm filing issues labelled as User story trying to capture the basic expected features.

If you have some recommendations on the format of those "user stories", feel free to share. My first try in #2 (closed) ended up not really as a user story but more like a formal specification... but I don't really want to over-specify in general, it's just that this one was trivial enough that I could afford the time to be relatively explicit.

I think we have at least the following features to draft with some details:

• Manage API tokens (#2 (closed))
• Register debusine workers (#4 (closed))
• Submit tasks to be executed (#5 (closed))
• Schedule and execute tasks on appropriate workers (#8 (closed))
• Monitor task status (#6 (closed))
• Implement the initial "sbuild" task (#7 (closed))