I'll have to think deeply about what this is doing. Initially, I read it as assigning a new user's role to an existing group's role; that's the opposite of what I want.
Thanks,
Rich
If it made you feel better, remember that CREATE USER is an alias for CREATE ROLE that includes LOGIN by default. So if you simply swap one word in your command, the context becomes a little more clear for what you want:
CREATE USER new_management_user [other stuff here]
