Allow @ and : in usernames when created by teacher

[boryanagoncharenko]

Describe the bug
Currently, when a teacher creates student accounts in bulk, they should not use the symbols @ and :. In this context, the invalid symbols seem to be a legacy. To replicate this, create a teacher account and class. Go to 'For teachers' tab > select a class > Click the 'Add Students' button > then click the 'Create accounts' button.

• Allow the @ to be used in usernames only when the teacher is creating student accounts. Note that the login page should keep the requirement to not use @.
• Investigate why the : was not allowed in the first place. Remote it, if it is legacy.

[abhi-github-159084]

I am interested to do this , please assign it to me.

[boryanagoncharenko]

I am interested to do this , please assign it to me.

Awesome! I updated the description and assigned the issue to you. Please feel free to reach out if you have questions or if you get stuck.