fix(fd): pay late-renewal gap interest to the linked Savings account, not the FD

Gap-period interest is earned at the linked account's rate, not the FD's --
folding it onto the FD's own balance meant "Re-Invest Maturity Amount"
silently carried savings interest into the new FD term as if it were FD
interest, and "Re-Invest Principal Only" paid it out through the FD's own
closure math instead of it already being where it belongs. Now posted
directly onto the linked account as its own INTEREST_POSTING transaction;
the FD's balance is left untouched, so every closure type renews/transfers
its real maturity amount. Renewal Preview updated to match (projectedBalance
is now just the FD's own balance) and now also returns the linked account's
own account number, so staff can see exactly where the gap interest is
about to land before confirming.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

fineract-provider/src/main/java/org/apache/fineract/portfolio/savings/service/DepositAccountWritePlatformServiceJpaRepositoryImpl.java

@@ -1704,9 +1704,11 @@ public class DepositAccountWritePlatformServiceJpaRepositoryImpl implements Depo
     /**
      * Read-only preview of what a Renew from the FD Dashboard is about to do, shown in the Payment
      * dialog before the staff member confirms anything -- the actual current balance, the linked
-     * account's rate, the gap-day count, the computed gap-interest amount, and the balance the FD will
-     * carry into its new term once that interest lands. Mirrors {@link #creditGapInterest} exactly but
-     * never posts anything; a within-grace account gets zero for the gap fields since nothing is owed.
+     * account's rate, the gap-day count, and the computed gap-interest amount. The gap interest is paid
+     * onto the LINKED savings account, not folded into the FD (see {@link #creditGapInterest}), so
+     * projectedBalance is just the FD's own current balance, unchanged by it -- what actually renews.
+     * Mirrors {@link #creditGapInterest} exactly but never posts anything; a within-grace account gets
+     * zero for the gap fields since nothing is owed.
      */
     @Transactional(readOnly = true)
     @Override
@@ -1750,12 +1752,15 @@ public class DepositAccountWritePlatformServiceJpaRepositoryImpl implements Depo
             result.put("projectedBalance", null);
             return result;
         }
+        result.put("linkedAccountNo", resolveLinkedAccountNo(linkedAccountId));
 
         final BigDecimal linkedAccountRate = resolveLinkedAccountRate(linkedAccountId);
         final BigDecimal gapInterestAmount = computeGapInterestAmount(fdAccount, linkedAccountRate, gapDays);
         result.put("linkedAccountRate", linkedAccountRate);
         result.put("gapInterestAmount", gapInterestAmount);
-        result.put("projectedBalance", currentBalance.add(gapInterestAmount));
+        // Paid onto the linked savings account, not this FD -- what renews is still just the FD's own
+        // current balance.
+        result.put("projectedBalance", currentBalance);
         return result;
     }
 
@@ -1790,6 +1795,13 @@ public class DepositAccountWritePlatformServiceJpaRepositoryImpl implements Depo
                 """, BigDecimal.class, linkedAccountId);
     }
 
+    /** Read fresh off the target account itself, same reasoning as {@link #resolveLinkedAccountId} --
+     *  shown in the Renewal Preview so staff can see exactly which account the gap interest is about
+     *  to land on, not just that "a linked account" exists. */
+    private String resolveLinkedAccountNo(final Long linkedAccountId) {
+        return this.jdbcTemplate.queryForObject("SELECT account_no FROM m_savings_account WHERE id = ?", String.class, linkedAccountId);
+    }
+
     /** Simple interest on the FD's own current balance, for the stretch between its maturity date and
      *  today, at the linked account's product rate -- the pure calculation, shared by the posting path
      *  ({@link #creditGapInterest}) and the read-only preview ({@link #previewFdRenewal}) so the number
@@ -1805,23 +1817,30 @@ public class DepositAccountWritePlatformServiceJpaRepositoryImpl implements Depo
 
     /**
      * Simple interest for the stretch between the FD's own maturity date and today, at the rate of its
-     * linked Savings/Current account's product -- credited onto the FD itself as a genuine
-     * INTEREST_POSTING transaction (not a DEPOSIT, which would wrongly count as cash received in the
-     * cashier/vault reconciliation) before whatever the caller does next (a manual renewal, or the FD
-     * Dashboard's generic Payment command) reads the account's balance. Shared by
-     * {@link #renewMaturedFixedDeposit} and {@link #creditGapInterestIfPastGrace} -- the FD Dashboard's
-     * Renew action now calls the latter as a pre-step before submitting the same generic `payment`
-     * command the account's own Account Actions menu already uses, so every closure type (Transfer to
-     * Savings, both Reinvest options, Partial Reinvest) is available from the Dashboard too, not just the
-     * two this method's sibling endpoint originally supported.
+     * linked Savings account's product -- credited onto the LINKED SAVINGS ACCOUNT, as a genuine
+     * INTEREST_POSTING transaction there (not a DEPOSIT, which would wrongly count as cash received in
+     * the cashier/vault reconciliation), rather than onto the FD itself. This interest was earned at
+     * the savings account's rate, not the FD's, so it belongs on that account's own ledger -- folding
+     * it into the FD's balance instead would mean "Re-Invest Maturity Amount" silently carries savings
+     * interest into the new FD term as if it were FD interest, and "Re-Invest Principal Only" would pay
+     * it out through the FD's own closure math instead of it already being where it belongs. The FD's
+     * own balance is left untouched by this call, so whatever the caller does next (a manual renewal, or
+     * the FD Dashboard's generic Payment command) reads the FD's real maturity balance, with the gap
+     * interest already sitting separately in the linked account. Shared by {@link #renewMaturedFixedDeposit}
+     * and {@link #creditGapInterestIfPastGrace} -- the FD Dashboard's Renew action now calls the latter as
+     * a pre-step before submitting the same generic `payment` command the account's own Account Actions
+     * menu already uses, so every closure type (Transfer to Savings, both Reinvest options, Partial
+     * Reinvest) is available from the Dashboard too, not just the two this method's sibling endpoint
+     * originally supported.
      */
     private BigDecimal creditGapInterest(final FixedDepositAccount fdAccount, final LocalDate maturityDate, final LocalDate today) {
         final Long linkedAccountId = resolveLinkedAccountId(fdAccount.getId());
         if (linkedAccountId == null) {
             throw new GeneralPlatformDomainRuleException("error.msg.fixeddepositaccount.renewal.linked.account.required",
-                    "This FD's grace period has passed and it has no Deposit Account Link -- link a Savings/Current account to it "
-                            + "before renewing late, so the gap-period interest has a rate to use.");
+                    "This FD's grace period has passed and it has no Deposit Account Link -- link a Savings account to it "
+                            + "before renewing late, so the gap-period interest has somewhere to be paid.");
         }
+        final SavingsAccount linkedAccount = this.depositAccountAssembler.assembleFrom(linkedAccountId, DepositAccountType.SAVINGS_DEPOSIT);
         final BigDecimal linkedAccountRate = resolveLinkedAccountRate(linkedAccountId);
         final long gapDays = ChronoUnit.DAYS.between(maturityDate, today);
         final BigDecimal gapInterestAmount = computeGapInterestAmount(fdAccount, linkedAccountRate, gapDays);
@@ -1829,14 +1848,14 @@ public class DepositAccountWritePlatformServiceJpaRepositoryImpl implements Depo
         if (gapInterestAmount.compareTo(BigDecimal.ZERO) > 0) {
             final Set<Long> existingTransactionIds = new HashSet<>();
             final Set<Long> existingReversedTransactionIds = new HashSet<>();
-            updateExistingTransactionsDetails(fdAccount, existingTransactionIds, existingReversedTransactionIds);
+            updateExistingTransactionsDetails(linkedAccount, existingTransactionIds, existingReversedTransactionIds);
 
-            final SavingsAccountTransaction gapInterestTxn = SavingsAccountTransaction.interestPosting(fdAccount, fdAccount.office(),
-                    today, Money.of(fdAccount.getCurrency(), gapInterestAmount), true);
-            fdAccount.addTransaction(gapInterestTxn);
-            fdAccount.updateSavingsAccountSummary(fdAccount.getTransactions());
-            this.savingAccountRepositoryWrapper.saveAndFlush(fdAccount);
-            postJournalEntries(fdAccount, existingTransactionIds, existingReversedTransactionIds);
+            final SavingsAccountTransaction gapInterestTxn = SavingsAccountTransaction.interestPosting(linkedAccount,
+                    linkedAccount.office(), today, Money.of(linkedAccount.getCurrency(), gapInterestAmount), true);
+            linkedAccount.addTransaction(gapInterestTxn);
+            linkedAccount.updateSavingsAccountSummary(linkedAccount.getTransactions());
+            this.savingAccountRepositoryWrapper.saveAndFlush(linkedAccount);
+            postJournalEntries(linkedAccount, existingTransactionIds, existingReversedTransactionIds);
         }
         return gapInterestAmount;
     }