Comment 5 for bug 1779717

"Presumably we only want to change the project and user id on a consumer record if it is either empty or has the sentinel values from CONF?"

Currently, those are the only two scenarios that make sense, yes.

I can certainly see a scenario in the future of "transferring ownership" of an instance (or volume or whatever) from one user or project to another. This has been something that has been requested for like 5 years in other OpenStack projects (ownership transfer) but we haven't done much about it.