Ability to validate usernames during creation

As a Crowd Admin
I want to be able to set a regex to validate usernames the same way I do for passwords
So that I can prevent usernames from containing special characters such as spaces

Summary

Customer reported in ticket that a user was created wrongly with a space character in the username. That prevented a connected application from synchronizing the Directory from that moment until the user was removed.

Workaround

For the moment the option is not available, so in such situation admins have to prevent it manually or recreate the users when created wrongly.