public CommandValidator(IUserValidator validator)
{
RuleFor(c => c.UserName).NotNull().NotEmpty();
RuleFor(c => c.Password).NotNull().NotEmpty();
RuleFor(c => c.UserName)
.MustAsync(async(command, userName, cancToken) =>
await validator.ValidUserAndPasswordAsync(command.Password, userName, CancellationToken.None))
.WithMessage(ErrorMessages.INVALID_USERNAME_OR_PASSWORD);
}