Balance metadata on typesense is empty after recording a transaction with the balance.

[stkegoul]

Describe the bug
When a balance performs a transaction, the Typesense upsert does not include the metadata field. As a result, when the balance is reindexed after the transaction, the existing metadata in Typesense is overwritten and becomes empty.

To Reproduce
Steps to reproduce the behavior:

1. Create two new balances:

curl -X POST 'http://localhost:5001/balances' \
-d '{
  "ledger_id": "general_ledger_id",
  "currency": "USD",
  "meta_data": {
    "field": "test_value"
  }
}'

2. Call search to confirm that the balances are indexed with the metadata

curl -X POST 'http://localhost:5001/search/balances' \
-d '{ "q": "*" }'

3. Create a transaction between both balances.

curl -X POST 'http://localhost:5001/transactions
-d '{
    "amount": 12091.12,
    "currency": "USD",
    "precision": 100,
    "reference": "ref-001",
    "source": "bln_19c0bcd8-e136-4a89-91b3-5be4066b68c4",
    "destination": "bln_a603ab29-7f3d-40f9-9752-8f04e197ddd9",
    "description": "Bug test",
    "allow_overdraft": true
}'

4. Check the balances via Search again.
5. You'll see that the balances' metadata is now empty/overwritten although other fields are correct.

Expected behavior
The metadata should persist when updating a balance record in Typesense after creating a transaction.

[danieljrassistant]

Root cause found (analyzed with AI assistance)

In database/balance.go, GetBalanceByIDLite() does not include meta_data in its SQL SELECT query:

SELECT balance_id, indicator, currency, currency_multiplier, ledger_id,
       balance, credit_balance, debit_balance, inflight_balance,
       inflight_credit_balance, inflight_debit_balance, created_at,
       version, track_fund_lineage, allocation_strategy, identity_id
FROM blnk.balances WHERE balance_id = $1
-- meta_data is missing!

In transaction.go, postTransactionActions() calls getSourceAndDestination() which uses GetBalanceByIDLite() by default. This returns a Balance struct with MetaData = nil. That object is then passed to batch.AddDependency("balances", ...) → Typesense upsert overwrites existing meta_data with empty/null.

Fix: Add meta_data to the SELECT in GetBalanceByIDLite() and scan it:

// 1. In GetBalanceByIDLite SQL query — add meta_data:
SELECT balance_id, indicator, ..., meta_data
FROM blnk.balances WHERE balance_id = $1

// 2. Add scan variable:
var metaDataJSON []byte

// 3. In row.Scan() — add:
&metaDataJSON,

// 4. After scan:
if len(metaDataJSON) > 0 {
    _ = json.Unmarshal(metaDataJSON, &balance.MetaData)
}

This ensures meta_data is preserved when balances are re-indexed after transactions.

---

This analysis was performed with the help of an AI coding assistant (Claude). The root cause was identified by tracing the call chain: postTransactionActions → getSourceAndDestination → GetBalanceByIDLite → missing meta_data in SQL SELECT.