Qualtrics Survey Xblock

  Author fields in Studio:
   - Display Name
   - Survey ID
   - Your University
   - Link Text
   - Parameter Name for UserID

  If Parameter Name is left blank, the anonymous student id is
  omitted from the url.

  Links to an already existing Qualtrics survey.
@jinpa That makes sense. I thought this field was static and didn't know
instructors freely use varying values here. I did, indeed, misunderstand the use case.

@dcadams Can you add a clarifying comment in the code, explaining the default
value of `a`? Or could the default instead be something like `uid` or
something? As is, this is a bit opaque to future developers.