fix: Allow multiple accounts per (party, org, instrument) - unblock nightly Demo Reset (#2174)

* fix: Allow multiple accounts per (party, org, instrument) for multi-service billing

Drops idx_account_syndicate_scope_integrity, the unique partial index on
(party_id, org_party_id, instrument_code) introduced in PRD-022. The original
constraint modelled a syndicate where each participant holds one position per
currency in a venture, but it does not match utility billing patterns where a
single customer legitimately holds separate billing accounts of the same
instrument with the same supplier (e.g. PPM-ELEC-CUST001 and PPM-GAS-CUST001
under the same supplier party for Margaret Thornton in the PAYG demo).

This has caused the nightly Demo Reset workflow to fail since the PAYG Energy
tenant was added on 2026-03-27 (#1963). With the index removed, account
uniqueness is still enforced by idx_account_account_identification, so the
constraint relaxation does not allow accidental duplication; it only allows
the legitimate multi-service-per-supplier pattern.

Updates the org-scoped migration test to assert the new behaviour (multiple
GBP accounts allowed per party+org, account_identification uniqueness still
enforced).

* test: Tighten duplicate-key assertion to verify constraint name

Per CodeRabbit review: assert.Error alone passes on any insert failure.
Tighten to require the failure references account_identification so the
test specifically proves uniqueness on that column survives dropping the
syndicate scope integrity index.

---------

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

Author: bjcoombs

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

@@ -73,11 +73,9 @@ func TestOrgScopedMigrations_CockroachDB(t *testing.T) {
 	})
 
 	t.Run("IndexesCreated", func(t *testing.T) {
-		// Verify the three indexes were created
 		for _, indexName := range []string{
 			"idx_account_participant_syndicate",
 			"idx_account_syndicate_participants",
-			"idx_account_syndicate_scope_integrity",
 		} {
 			var count int64
 			err := gormDB.Raw(`
@@ -89,6 +87,20 @@ func TestOrgScopedMigrations_CockroachDB(t *testing.T) {
 		}
 	})
 
+	t.Run("ScopeIntegrityIndexDropped", func(t *testing.T) {
+		// Migration 20260416000001 dropped idx_account_syndicate_scope_integrity to allow
+		// multiple accounts per (party_id, org_party_id, instrument_code) — required by
+		// utility billing patterns (e.g. separate GBP accounts for electricity and gas
+		// from the same supplier).
+		var count int64
+		err := gormDB.Raw(`
+			SELECT COUNT(*) FROM pg_indexes
+			WHERE tablename = 'account' AND indexname = 'idx_account_syndicate_scope_integrity'
+		`).Scan(&count).Error
+		require.NoError(t, err)
+		assert.Equal(t, int64(0), count, "idx_account_syndicate_scope_integrity should have been dropped")
+	})
+
 	t.Run("CanCreateOrgScopedAccount", func(t *testing.T) {
 		partyID := uuid.New()
 		orgPartyID := uuid.New()
@@ -149,16 +161,18 @@ func TestOrgScopedMigrations_CockroachDB(t *testing.T) {
 		assert.Nil(t, retrieved.OrgPartyID, "Personal account should have NULL org_party_id")
 	})
 
-	t.Run("UniqueConstraintOnPartyOrgInstrumentCode", func(t *testing.T) {
+	t.Run("MultipleAccountsPerPartyOrgInstrumentAllowed", func(t *testing.T) {
+		// Utility billing case: a customer has separate GBP billing accounts for electricity
+		// and gas with the same supplier. After migration 20260416000001, both succeed and
+		// uniqueness is preserved only by account_identification.
 		partyID := uuid.New()
 		orgPartyID := uuid.New()
 		now := time.Now()
 
-		// First account: party + org + GBP
 		entity1 := &CurrentAccountEntity{
 			ID:                    uuid.New(),
 			AccountID:             "ACC-UNIQ-001",
-			AccountIdentification: "GB82WEST33333333333333",
+			AccountIdentification: "PPM-ELEC-DEMO-001",
 			AccountType:           "current",
 			InstrumentCode:        "GBP",
 			Dimension:             "CURRENCY",
@@ -172,13 +186,12 @@ func TestOrgScopedMigrations_CockroachDB(t *testing.T) {
 			UpdatedBy:             "system",
 		}
 		err := gormDB.Create(entity1).Error
-		require.NoError(t, err, "First org-scoped account should succeed")
+		require.NoError(t, err, "First org-scoped GBP account should succeed")
 
-		// Duplicate: same party + org + instrument_code should fail
 		entity2 := &CurrentAccountEntity{
 			ID:                    uuid.New(),
 			AccountID:             "ACC-UNIQ-002",
-			AccountIdentification: "GB82WEST44444444444444",
+			AccountIdentification: "PPM-GAS-DEMO-001",
 			AccountType:           "current",
 			InstrumentCode:        "GBP",
 			Dimension:             "CURRENCY",
@@ -192,13 +205,12 @@ func TestOrgScopedMigrations_CockroachDB(t *testing.T) {
 			UpdatedBy:             "system",
 		}
 		err = gormDB.Create(entity2).Error
-		assert.Error(t, err, "Duplicate (party_id, org_party_id, instrument_code) should be rejected by unique index")
+		assert.NoError(t, err, "Second GBP account for same (party, org) should succeed (multi-service billing)")
 
-		// Different instrument_code: same party + org + EUR should succeed
 		entity3 := &CurrentAccountEntity{
 			ID:                    uuid.New(),
 			AccountID:             "ACC-UNIQ-003",
-			AccountIdentification: "GB82WEST55555555555555",
+			AccountIdentification: "PPM-EUR-DEMO-001",
 			AccountType:           "current",
 			InstrumentCode:        "EUR",
 			Dimension:             "CURRENCY",
@@ -213,6 +225,28 @@ func TestOrgScopedMigrations_CockroachDB(t *testing.T) {
 		}
 		err = gormDB.Create(entity3).Error
 		assert.NoError(t, err, "Different instrument_code for same (party_id, org_party_id) should succeed")
+
+		// Account-identifier uniqueness is still enforced by idx_account_account_identification.
+		dup := &CurrentAccountEntity{
+			ID:                    uuid.New(),
+			AccountID:             "ACC-UNIQ-004",
+			AccountIdentification: "PPM-ELEC-DEMO-001",
+			AccountType:           "current",
+			InstrumentCode:        "GBP",
+			Dimension:             "CURRENCY",
+			Status:                "active",
+			PartyID:               partyID,
+			OrgPartyID:            &orgPartyID,
+			OverdraftLimit:        0,
+			CreatedAt:             now,
+			UpdatedAt:             now,
+			CreatedBy:             "system",
+			UpdatedBy:             "system",
+		}
+		err = gormDB.Create(dup).Error
+		require.Error(t, err, "Duplicate account_identification must still be rejected")
+		assert.Contains(t, err.Error(), "duplicate key", "rejection should be a uniqueness violation")
+		assert.Contains(t, err.Error(), "account_identification", "rejection must reference idx_account_account_identification, not some other constraint")
 	})
 
 	t.Run("UniqueConstraintDoesNotAffectPersonalAccounts", func(t *testing.T) {

services/current-account/migrations/20260416000001_drop_syndicate_scope_integrity_index.sql

@@ -0,0 +1,15 @@
+-- Drop idx_account_syndicate_scope_integrity (party_id, org_party_id, instrument_code).
+--
+-- The original constraint (PRD-022) assumed one account per party per organisation per
+-- currency, modelled on a syndicate where Alice holds a single GBP position in Venture Alpha.
+-- That assumption does not hold for utility billing or any multi-service scenario where a
+-- party legitimately holds multiple instrument-equivalent accounts under the same supplier:
+-- a residential customer needs separate GBP billing accounts for electricity and gas at the
+-- same supplier, and the same shape extends to multi-site customers (one billing account per
+-- premise) and multi-product offerings.
+--
+-- Account-identifier uniqueness is preserved by idx_account_account_identification, so
+-- dropping this index does not allow accidental account duplication; it only allows the
+-- legitimate "Margaret has GBP-elec and GBP-gas with Utilita" pattern.
+
+DROP INDEX IF EXISTS "idx_account_syndicate_scope_integrity";

services/current-account/migrations/atlas.sum

@@ -1,4 +1,4 @@
-h1:PnPRafxLtbQAhHssRdEu02xkP/eQb96IF7HwUpVmYvE=
+h1:C1bgEjVoS7bhttB5ntNjdmFCKz9yaBltHLl5kwGkbXk=
 20251216000001_initial.sql h1:nyRf35O3eYNJqShAvOEhvliXKLIR6e/V8B9JhOHde9w=
 20251216000002_audit_system.sql h1:X/0ZHt9cGTYmFbUUvKAkBgEiGw9fYEqfnbMB8I4SCR8=
 20251217000001_fix_audit_status_constraint.sql h1:yQxsHxbUp5g+ehkKFjOhZs59SbfaQIPw4/sA2xE2rwU=
@@ -28,3 +28,4 @@ h1:PnPRafxLtbQAhHssRdEu02xkP/eQb96IF7HwUpVmYvE=
 20260316000002_add_event_outbox_tenant_id_index.sql h1:hrEPnXoHQ1bnaMtvFFwZ9UzJVtryQrIe6zDSDqfoLbM=
 20260323000001_align_audit_schema.sql h1:AmTi2tik7qBcMVH589i0pvv14DxTbPMbK0w24n0aw+g=
 20260323000002_align_audit_schema_data.sql h1:5AqTImsCsnJIDldKPVAxFCwmb/8uabn7KZULF/PzQs8=
+20260416000001_drop_syndicate_scope_integrity_index.sql h1:S9u8OUer3WusmW31j2zAsNGaZRwMV3v6+BxA5k0FxDk=