WIP: Cleanup user vs userid

[ale-rt]

It might be a good idea before releasing major version to properly remove the ambiguity between user and userid

This is missing the mandatory upgrade step.
I will had it if there is actually some interest in resolving this naming issue.

[davisagli]

I like this goal, but I'm also worried that when refactoring code that uses collective.workspace, it will be easy to overlook calls to add_to_team or update which are still using user. And as currently written, the failure mode then would be to store data in the wrong key, rather than to raise an exception so that the developer realizes something needs to be updated. Can we deprecate user by making use of it raise an exception for a while?

[ale-rt]

It is definitely a good idea :) I will put a WIP in the title for the moment, then I will implement this deprecation.
Anyway this is very low prio