JIRA username and email fields have different valid characters

Background
The JIRA username field has different valid characters than the email field. This creates an unfriendly situation when you add a customer in JSD. When you invite/add a new customer to JSD from the customers page, JSD creates the user using the email address as a username. If you invite/add the new customer from User Management, you can choose a different username.

Scenario
1. In JSD project Customers page, Agent invites/adds customer using an email address that contains characters that are not valid in the username field (e.g. &). JSD tries to use the email address as the username, and can't because the username field does not allow &.
2. Dialog throws the following err: Email address contains characters that aren’t valid in the username. Add the user, then use the username to add the user to the project. (Add the user is a CTA to User Management)
3. User has to go to UM, add the user, then go back to the project & invite the user using the username instead of the email.

This is confusing & also a pain because you have to leave your task, to go UM, then go back to your task.