Add UniqueField Constraint to Display Name

Don't translate the message when adding the constraint. This will be done in the validate method of UniqueFieldValueValidator

Thank you. #3 works fine.

Thank you but this defeats the purpose of this module which is to provide an unconstrained field for the displayed user name. If uniqueness is needed then there is already the default user name field.

If this is made optional, then I'll reconsider it.

Hi Orakili,
thanks for the new D11 compatible release!

as for this issue, i understand that this is against the purpose of this module.
but there is an additional use case for having user display name different from username, which is not exposing login name for other users.
i agree having this optional would be a good idea!

I agree with #6, +1 to this issue.