Automatically login to tableau without disclosing user name and password to my participants?

Hello,
as a part of an experiment I'd like participants to access and interact with a tableau dashboard, embedded into Qualtrics via an iframe. Problem is, they'd need an account and login. I don't want and cannot openly share the account credentials for them to login manually.
Can I automatically log them in with valid account credentials, without disclosing them? I'm picturing coding something so that the login data would be sent to tableau and they'd be logged in. I read something about POST requests, is that the way to go?

I am a complete beginner, I hope this is feasible. If it is but too complex to explain in detail, I'd appreciate some resources that I could use to learn.