Error Message When Changing Username

Hello, ## Description: I have found a bug in your fix other my other report, #243609. I reported this in a new report as this is an error in the error message. When changing your username that starts with a `.` the error message is: `Username may only contain letters, numbers or the following characters: @ . + - _` A normal user would be confused as it does not state any reason for the `.` not being allowed at the beginning of their username. ## POC: 1. Change your username to a name that starts with a `.`. 2. You will receive an error message that does not explain why this is not excepted. ## Mitigation: I recommend you add a specific error message that states that your username cannot start with a `.`. Thanks!