Explain when a username cannot be changed

[matt-west]

Where

/me

Problem

Some users don’t appear to be able to change their username, but we don’t explain why this field is disabled.

Solution

Add a note or tooltip to the field explaining why the username cannot be changed.

[github-actions]

OpenAI suggested the following labels for this issue:

• [Feature Group] User Management: This issue relates to managing user accounts, specifically the ability to change usernames.
• [Feature] User & Account Settings (/me): The content specifically addresses the username field in user account settings.
• [Feature] Help Center: The suggested solution involves providing help or tooltips to assist users with understanding username change limitations.