Hey Michael -
Ultimately, it sounds like you want to allow a single username string to be used by multiple users and have it automagically "uniqufiy" based on the site(s) it is associated with. As you point out, this is problematic on a number of levels:
The username is a proxy/pointer to site or sites it is associated with. To remove this relationship and allow for multiple people to share the same username string on the same system, then you need some way to internally modify the username so that when someone presents the username "Russell", we know whether we're talking about the "Russell" (system user 123) in Site1, the "Russell" (system user 912), in Site2, or the "Russell" (system user 763) in Site3.
I guess this could be accomplished by having a distinct login page for each site:
- Russell logging in at /auth1 gets mapped to user 123
- Russell logging in at /auth2 gets mapped to user 912
- Russell logging in at /auth3 gets mapped to user 763
...but Tableau doesn't do this. It would be a mess
Tableau Online approaches this problem by making the person's username the email address on their tableausoftware.com account. Maybe you should do the same thing? That way the user still gets a "personalized" username without giving them a real choice and having multiple people try and use the string "Russell".
That's exactly what I'm looking for. Right now, my solution was to "prefix" the usernames by the site-id or something along the way, but I wanted to know how it is addressed with Tableau Online.
Using the email address is actually a surprisingly simple yet efficient solution. The uniqueness of email address is something I believe we could rely on in our context.