Use enum directly for over-applied calculation type instead of string comparison

- Restore enum import: LoanOverAppliedCalculationType
- Replace string comparison with proper enum conversion using .valueOf()
- Use .toUpperCase() (ASCII, no Locale needed) to map 'percentage' → 'PERCENTAGE'
- Call .isPercentage() on enum for type-safe, idiomatic domain model usage
- Maintains compile-time safety and respects Fineract design patterns

Author: P-ragati

fineract-provider/src/main/java/org/apache/fineract/portfolio/loanaccount/serialization/LoanDisbursementValidator.java

@@ -25,6 +25,7 @@
 import org.apache.fineract.infrastructure.core.service.MathUtil;
 import org.apache.fineract.organisation.monetary.domain.MoneyHelper;
 import org.apache.fineract.portfolio.loanaccount.domain.Loan;
+import org.apache.fineract.portfolio.loanaccount.domain.LoanOverAppliedCalculationType;
 import org.apache.fineract.portfolio.loanproduct.domain.LoanProduct;
 import org.apache.fineract.portfolio.loanaccount.exception.InvalidLoanStateTransitionException;
 import org.apache.fineract.portfolio.loanaccount.exception.LoanDisbursalException;
@@ -70,8 +71,10 @@ private BigDecimal calculateMaxAllowedDisbursement(final Loan loan) {
 
         if (loanProduct.getOverAppliedCalculationType() != null && loanProduct.getOverAppliedNumber() != null) {
             final BigDecimal overAppliedMax = BigDecimal.valueOf(loanProduct.getOverAppliedNumber());
+            final LoanOverAppliedCalculationType calculationType = LoanOverAppliedCalculationType
+                    .valueOf(loanProduct.getOverAppliedCalculationType().toUpperCase());
 
-            if ("percentage".equalsIgnoreCase(loanProduct.getOverAppliedCalculationType())) {
+            if (calculationType.isPercentage()) {
                 final BigDecimal extra = MathUtil.percentageOf(approvedPrincipal, overAppliedMax, MoneyHelper.getMathContext());
                 maxAllowed = approvedPrincipal.add(extra);
             } else {