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-provider/src/main/resources/db/changelog/tenant/changelog-tenant.xml

@@ -313,4 +313,6 @@
     <include file="parts/0294_add_tfa_token_to_dsc_challenge.xml" relativeToChangelogFile="true"/>
     <include file="parts/0295_unique_email_mobile_on_m_appuser.xml" relativeToChangelogFile="true"/>
     <include file="parts/0296_unique_nominee_per_account_type.xml" relativeToChangelogFile="true"/>
+    <include file="parts/0297_fix_unique_nominee_per_account.xml" relativeToChangelogFile="true"/>
+    <include file="parts/0298_unique_external_id_on_current_account.xml" relativeToChangelogFile="true"/>
 </databaseChangeLog>

fineract-provider/src/main/resources/db/changelog/tenant/parts/0297_fix_unique_nominee_per_account.xml

@@ -0,0 +1,47 @@
+<?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. The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License. You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+-->
+<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">
+
+    <!--
+        Fix: previous constraint uq_client_nominee_per_account_type was on
+        (client_id, nominee_client_id, account_type) — this incorrectly blocked the
+        same nominee from being added to multiple accounts of the same type
+        (e.g. two SB accounts). The correct uniqueness is per individual account:
+        (client_id, nominee_client_id, account_no, account_type).
+    -->
+    <changeSet id="0297_fix_unique_nominee_per_account" author="fineract" dbms="postgresql">
+        <preConditions onFail="MARK_RAN">
+            <tableExists tableName="m_client_nominee"/>
+        </preConditions>
+        <sql>
+            DROP INDEX IF EXISTS uq_client_nominee_per_account_type;
+
+            CREATE UNIQUE INDEX IF NOT EXISTS uq_client_nominee_per_account
+            ON m_client_nominee (client_id, nominee_client_id, account_no, account_type)
+            WHERE is_deleted = false;
+        </sql>
+        <rollback>
+            <sql>
+                DROP INDEX IF EXISTS uq_client_nominee_per_account;
+
+                CREATE UNIQUE INDEX IF NOT EXISTS uq_client_nominee_per_account_type
+                ON m_client_nominee (client_id, nominee_client_id, account_type)
+                WHERE is_deleted = false;
+            </sql>
+        </rollback>
+    </changeSet>
+
+</databaseChangeLog>

fineract-provider/src/main/resources/db/changelog/tenant/parts/0298_unique_external_id_on_current_account.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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="0298_unique_external_id_on_current_account" author="CBS">
+        <preConditions onFail="MARK_RAN">
+            <tableExists tableName="m_current_account"/>
+            <not><indexExists tableName="m_current_account" indexName="ca_external_id_UNIQUE"/></not>
+            <not><indexExists tableName="m_current_account" indexName="ca_unq_external_id"/></not>
+        </preConditions>
+        <addUniqueConstraint
+            tableName="m_current_account"
+            columnNames="external_id"
+            constraintName="ca_external_id_UNIQUE"/>
+    </changeSet>
+
+</databaseChangeLog>