Non-Userfriendly error message when using non-allowed characters in profile username

[FlyingPig69]

Steps to recreate:

1. Edit your profile username to "Flying_Pig"

Error message: "{"detail":[{"loc":["body","name"],"msg":"'Flying_Pig' is not restricted to 'QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm1234567890'","type":"value_error"}]}"

Removing the _ enables the name to be saved.

[esot321c]

Bounty: improve error messages and form validation visualization

[svgor-code]

@esot321c assign me please