It has long been a function to have an owner of the tracker item, but
what if other users want to "join" - add their names to that tracker
item. Use cases would be like todo lists, "liking" an item etc.
Subscribing for updates . . .
plus, linking it to the user tracker would be good, and being able to
report lists of items with joined members.
I think the watch function is approaching this - might have to modify
the UI somewhat.
Any comments or suggestions welcome.