public CommandValidator(IUserValidator validator)
{
RuleFor(c => c.UserName).NotNull().NotEmpty();
RuleFor(c => c.UserName)
.MustAsync(validator.NameNotTakenAsync).WithMessage(ErrorMessages.USERNAME_ALREADY_TAKEN);
RuleFor(c => c.FirstName).NotNull().NotEmpty();
RuleFor(c => c.Password).NotNull().NotEmpty();
RuleFor(c => c.ConfirmedPassword)
.Must((command, confirmedPassword) => validator.PasswordMatchesConfirmation(command.Password, confirmedPassword))
.WithMessage(ErrorMessages.PASSWORDS_DONT_MATCH);
}