public Proposal Validate(Proposal proposal)
        {
            BaseValidator validatorChain = new LoanValueValidator();

            validatorChain
            .SetNext(new LoanMonthlyInStallmentsValidator())
            .SetNext(new MinimumProponentQuantityValidator())
            .SetNext(new MainProponentQuantityValidator())
            .SetNext(new ProponentAgeValidator())
            .SetNext(new WarrantyQuantityValidator())
            .SetNext(new WarrantyValueValidator())
            .SetNext(new WarrantyStateValidator())
            .SetNext(new ProponentIncomeValidator());

            validatorChain.Validate(proposal);

            return(proposal.AsInvalid());
        }