feat: multi-nominee support, duplicate validation, and FD/RD required fields

Account Creation Enhancements:
- Added multi-nominee support for SB, CA, FD, RD accounts (nominees[] array)
- Backend: saveNomineesIfPresent() validates total share <= 100% before saving
- Added 'nominees' to parameter whitelists (SavingsAccountConstant, DepositsApiConstants)

Duplicate Validation Fixes:
- SB/FD/RD: Fixed duplicate externalId error handler to walk full exception cause
  chain (EclipseLink wraps PSQLException deep) — now matches constraint
  'm_savings_account_external_id_key' and returns proper 400 error
- CA: Added try-catch around both saveAndFlush calls for duplicate externalId
  (constraint: ca_unq_external_id) with throwIfDuplicateExternalId() helper
- CA: Added duplicate product check — blocks creating same product twice for client
- SB/FD/RD: Added JpaSystemException handling via getAllCauseMessages() helper

Current Account (CA) Improvements:
- CurrentAccount entity: added @UniqueConstraint for external_id (ca_unq_external_id)
- CurrentAccountRepository: added countActiveByClientAndProduct() JPQL query
- Liquibase 0298: unique constraint on m_current_account.external_id

FD/RD Required Field Validation (Backend):
- DepositAccountDataValidator: depositPeriod now required for RD (was FD-only)
- DepositAccountDataValidator: mandatoryRecommendedDepositAmount now notNull+positive for RD
- DepositAccountDataValidator: customerSegment now required (notBlank) for both FD and RD

Liquibase Migrations:
- 0297: fix unique nominee per account constraint
- 0298: unique external_id on m_current_account
- 2014: add is_mandatory column to m_savings_account_joint_holders

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fineract-core/src/main/java/org/apache/fineract/portfolio/client/domain/ClientNomineeRepository.java

@@ -53,6 +53,17 @@ public interface ClientNomineeRepository extends JpaRepository<ClientNominee, Lo
             @Param("nomineeClientId") Long nomineeClientId,
             @Param("accountType") String accountType);
 
+    @Query("SELECT COUNT(n) FROM ClientNominee n "
+            + "WHERE n.client.id = :clientId "
+            + "AND n.nomineeClient.id = :nomineeClientId "
+            + "AND n.accountNo = :accountNo "
+            + "AND n.accountType = :accountType "
+            + "AND n.isDeleted = false")
+    long countActiveByClientNomineeAndAccountNoAndType(@Param("clientId") Long clientId,
+            @Param("nomineeClientId") Long nomineeClientId,
+            @Param("accountNo") String accountNo,
+            @Param("accountType") String accountType);
+
     @Query("SELECT COUNT(n) FROM ClientNominee n "
             + "WHERE n.client.id = :clientId "
             + "AND n.nomineeClient.id = :nomineeClientId "

fineract-core/src/main/java/org/apache/fineract/portfolio/savings/DepositsApiConstants.java

@@ -537,6 +537,7 @@ public final class DepositsApiConstants {
         fixedDepositRequestData.add(SavingsApiConstants.introducerNameParamName);
         fixedDepositRequestData.add(SavingsApiConstants.introducerCifNumberParamName);
         fixedDepositRequestData.add(SavingsApiConstants.nomineeParamName);
+        fixedDepositRequestData.add("nominees");
         fixedDepositRequestData.add(SavingsApiConstants.linkedAccountIdParamName);
         fixedDepositRequestData.add(SavingsApiConstants.linkedAccountTypeParamName);
         fixedDepositRequestData.add(SavingsApiConstants.linkedAccountNoParamName);
@@ -603,6 +604,7 @@ public final class DepositsApiConstants {
         recurringDepositRequestData.add(SavingsApiConstants.introducerNameParamName);
         recurringDepositRequestData.add(SavingsApiConstants.introducerCifNumberParamName);
         recurringDepositRequestData.add(SavingsApiConstants.nomineeParamName);
+        recurringDepositRequestData.add("nominees");
         recurringDepositRequestData.add(SavingsApiConstants.linkedAccountIdParamName);
         recurringDepositRequestData.add(SavingsApiConstants.linkedAccountTypeParamName);
         recurringDepositRequestData.add(SavingsApiConstants.linkedAccountNoParamName);