Setup Wizard ignores an invalid username in "Admin Info" step

[tassoevan]

Description:

Usernames which don't follow the default UTF8_Names_Validation regular expression ([0-9a-zA-Z-_.]+) in "Admin Info" step of Setup Wizard are ignored until the wizard finishes, where a "Register Username" modal appears.

Steps to reproduce:

1. In a fresh install, open the Setup Wizard;
2. Input a username that doesn't match the UTF8_Names_Validation settings (suggested: #####);
3. Fill out the "Admin Info" form with the additional requested info;
4. Click "Continue".

Expected behavior:

An error message is shown below the Username input and the Setup Wizard remains in the "Admin Info" step.

Actual behavior:

A error notification username-invalid is shown in the upper right corner of the browser viewport and the Setup Wizard advances to the next step.

Server Setup Information:

• Version of Rocket.Chat Server: 0.66.0-develop
• Operating System: Linux
• Deployment Method: all
• Number of Running Instances: 1
• DB Replicaset Oplog: enabled
• NodeJS Version: 8.11.1 - x64
• MongoDB Version: 3.4