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-savings/src/main/resources/db/changelog/tenant/module/savings/parts/module-changelog-master.xml

@@ -36,4 +36,5 @@
   <include file="parts/2011_add_facility_charge_mapping.xml" relativeToChangelogFile="true" />
   <include file="parts/2012_add_current_account_permissions.xml" relativeToChangelogFile="true" />
   <include file="parts/2013_add_missing_current_account_columns.xml" relativeToChangelogFile="true" />
+  <include file="parts/2014_add_is_mandatory_to_joint_holders.xml" relativeToChangelogFile="true" />
 </databaseChangeLog>

fineract-savings/src/main/resources/db/changelog/tenant/module/savings/parts/parts/2014_add_is_mandatory_to_joint_holders.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements. See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.
+-->
+<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
+                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                   xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-4.1.xsd">
+
+    <changeSet id="2014_add_is_mandatory_to_joint_holders" author="CBS">
+        <preConditions onFail="MARK_RAN">
+            <tableExists tableName="m_savings_account_joint_holders"/>
+            <not><columnExists tableName="m_savings_account_joint_holders" columnName="is_mandatory"/></not>
+        </preConditions>
+        <addColumn tableName="m_savings_account_joint_holders">
+            <column name="is_mandatory" type="BOOLEAN" defaultValueBoolean="false">
+                <constraints nullable="false"/>
+            </column>
+        </addColumn>
+    </changeSet>
+
+</databaseChangeLog>