refactor: update current account domain model for instrument-based quantities (#1213)

* refactor: update current account domain model for instrument-based quantities

- Add instrumentCode and dimension fields with accessors InstrumentCode(), Dimension()
- Rename accountIdentification to externalIdentifier; add ExternalIdentifier() accessor
- Keep AccountIdentification() as deprecated alias for backward compatibility
- Remove overdraft fields and methods (overdraftLimit, overdraftEnabled, overdraftRate,
  SetOverdraftLimit, UpdateOverdraftSettings); overdraft is now product-type behavior
- Update NewCurrentAccount() constructor: currency string replaced by instrumentCode, dimension
- Add NewCurrentAccountWithDimension() for explicit dimension specification
- Update CurrentAccountBuilder with WithInstrumentCode(), WithDimension(), WithExternalIdentifier()
- Update persistence layer: toDomain/toEntity use new fields, zero-out legacy overdraft columns
- Update service layer: remove overdraft logic, use ExternalIdentifier() and InstrumentCode()
- Update all saga orchestrators to use account.ExternalIdentifier() in saga inputs

* fix: address CodeRabbit review findings in current account domain model

- Clarify NewCurrentAccountWithDimension docstring: CURRENCY-only constraint is
  intentional for now (enforced by NewMoneyFromInstrument); non-currency support
  is deferred pending Money type generalisation in later tasks
- Handle Compare error explicitly in PrepareForDebit and Withdraw instead of
  discarding with blank identifier; error is unreachable (currency already verified)
  but should not be silently swallowed

* fix: address second round of CodeRabbit review findings

- Fix NewCurrentAccount docblock: remove stale dimension parameter mention;
  document that dimension defaults to CURRENCY
- Normalize dimension to uppercase in NewCurrentAccountWithDimension so
  Dimension() always returns canonical form (e.g. "currency" → "CURRENCY")
- Normalize dimension to uppercase in CurrentAccountBuilder.WithDimension
  for consistency

* docs: tighten current account domain comments to reflect CURRENCY-only constraint

Remove kWh/ELECTRICITY examples from InstrumentCode, Dimension, and WithDimension
docstrings; update inline docs to clearly state that only CURRENCY dimension is
currently supported, avoiding misleading callers about non-currency capabilities

---------

Co-authored-by: Ben Coombs <bjcoombs@users.noreply.github.com>

Author: bjcoombs

services/current-account/adapters/persistence/repository.go

@@ -653,16 +653,16 @@ func toEntity(ctx context.Context, account domain.CurrentAccount) (*CurrentAccou
 	// in-memory round-trip. Position Keeping is now the source of truth for balances.
 	return &CurrentAccountEntity{
 		ID:                    account.ID(),
-		AccountID:             account.AccountID(),             // Business account identifier
-		AccountIdentification: account.AccountIdentification(), // IBAN stored in account_identification
-		AccountType:           "current",                       // Default for current accounts
-		InstrumentCode:        account.Balance().CurrencyCode(),
-		Dimension:             account.Balance().Quantity().Instrument.Dimension,
+		AccountID:             account.AccountID(),          // Business account identifier
+		AccountIdentification: account.ExternalIdentifier(), // IBAN stored in account_identification
+		AccountType:           "current",                    // Default for current accounts
+		InstrumentCode:        account.InstrumentCode(),
+		Dimension:             account.Dimension(),
 		Status:                string(account.Status()),
 		PartyID:               partyUUID,
 		OrgPartyID:            account.OrgPartyID(),
-		OverdraftLimit:        account.OverdraftLimit().ToMinorUnitsUnchecked(),
-		OverdraftRate:         account.OverdraftRate(),
+		OverdraftLimit:        0, // Overdraft is now product-type behavior, not domain state
+		OverdraftRate:         0, // Overdraft is now product-type behavior, not domain state
 		ProductTypeCode:       productTypeCode,
 		ProductTypeVersion:    productTypeVersion,
 		Balance:               account.Balance().ToMinorUnitsUnchecked(),          // gorm:"-" - not persisted
@@ -678,7 +678,6 @@ func toEntity(ctx context.Context, account domain.CurrentAccount) (*CurrentAccou
 }
 
 // toDomain converts database entity to domain model using the builder pattern.
-// Note: OverdraftEnabled is derived from OverdraftLimit > 0
 // Note: Balance fields are not persisted - balance computation delegated to Position Keeping service.
 // The service layer is responsible for populating balance from Position Keeping after retrieval.
 func toDomain(entity *CurrentAccountEntity) (domain.CurrentAccount, error) {
@@ -695,14 +694,6 @@ func toDomain(entity *CurrentAccountEntity) (domain.CurrentAccount, error) {
 		return domain.CurrentAccount{}, fmt.Errorf("failed to create available balance: %w", err)
 	}
 
-	overdraftLimit, err := domain.NewMoneyFromInstrument(entity.InstrumentCode, entity.Dimension, entity.OverdraftLimit)
-	if err != nil {
-		return domain.CurrentAccount{}, fmt.Errorf("failed to create overdraft limit from database: %w", err)
-	}
-
-	// Derive overdraft enabled from limit > 0
-	overdraftEnabled := entity.OverdraftLimit > 0
-
 	// Balance is now computed by Position Keeping service, so use current time as placeholder.
 	// The service layer will update this when fetching balance from Position Keeping.
 	balanceUpdatedAt := entity.UpdatedAt
@@ -744,17 +735,16 @@ func toDomain(entity *CurrentAccountEntity) (domain.CurrentAccount, error) {
 	return domain.NewCurrentAccountBuilder().
 		WithID(entity.ID).
 		WithAccountID(entity.AccountID).
-		WithAccountIdentification(entity.AccountIdentification).
+		WithExternalIdentifier(entity.AccountIdentification).
+		WithInstrumentCode(entity.InstrumentCode).
+		WithDimension(entity.Dimension).
 		WithPartyID(entity.PartyID.String()).
 		WithOrgPartyID(entity.OrgPartyID).
 		WithBalance(balance).
 		WithAvailableBalance(availableBalance).
 		WithStatus(domain.AccountStatus(entity.Status)).
 		WithFreezeReason(freezeReason).
 		WithStatusHistory(statusHistory).
-		WithOverdraftLimit(overdraftLimit).
-		WithOverdraftEnabled(overdraftEnabled).
-		WithOverdraftRate(entity.OverdraftRate).
 		WithBalanceUpdatedAt(balanceUpdatedAt).
 		WithVersion(entity.Version).
 		WithCreatedAt(entity.CreatedAt).

services/current-account/adapters/persistence/repository_contract_test.go

@@ -49,7 +49,7 @@ func TestFindByID_UsesAccountID(t *testing.T) {
 	found, err := repo.FindByID(ctx, accountID)
 	require.NoError(t, err, "FindByID with account_id should succeed")
 	assert.Equal(t, accountID, found.AccountID())
-	assert.Equal(t, accountIdentification, found.AccountIdentification())
+	assert.Equal(t, accountIdentification, found.ExternalIdentifier())
 
 	// FindByID with IBAN should NOT find the account (it's not searching that column)
 	_, err = repo.FindByID(ctx, accountIdentification)

services/current-account/adapters/persistence/repository_test.go

@@ -207,8 +207,8 @@ func TestFindByIBAN(t *testing.T) {
 	if retrieved.AccountID() != accountID {
 		t.Errorf("Expected AccountID %s, got %s", accountID, retrieved.AccountID())
 	}
-	if retrieved.AccountIdentification() != iban {
-		t.Errorf("Expected IBAN %s, got %s", iban, retrieved.AccountIdentification())
+	if retrieved.ExternalIdentifier() != iban {
+		t.Errorf("Expected IBAN %s, got %s", iban, retrieved.ExternalIdentifier())
 	}
 }