Organize backend into product executable and shared Go modules

backend/shared/database/transaction/context.go

@@ -0,0 +1,12 @@
+package transaction
+
+import (
+	"context"
+
+	"go.mongodb.org/mongo-driver/v2/mongo"
+)
+
+func ActiveMongoTransaction(ctx context.Context) bool {
+	session := mongo.SessionFromContext(ctx)
+	return session != nil && session.TransactionRunning()
+}

backend/shared/database/transaction/context_test.go

@@ -0,0 +1,21 @@
+package transaction
+
+import (
+	"context"
+	"testing"
+
+	"go.mongodb.org/mongo-driver/v2/mongo"
+)
+
+func TestActiveMongoTransactionRejectsContextWithoutSession(t *testing.T) {
+	if ActiveMongoTransaction(context.Background()) {
+		t.Fatal("context without mongo session must not be active")
+	}
+}
+
+func TestActiveMongoTransactionRejectsSessionWithoutTransaction(t *testing.T) {
+	ctx := mongo.NewSessionContext(context.Background(), &mongo.Session{})
+	if ActiveMongoTransaction(ctx) {
+		t.Fatal("session without transaction must not be active")
+	}
+}

backend/shared/database/transaction/factory.go

@@ -0,0 +1,5 @@
+package transaction
+
+type Factory interface {
+	CreateTransaction() Transaction
+}

backend/shared/database/transaction/transaction.go

@@ -0,0 +1,11 @@
+package transaction
+
+import (
+	"context"
+)
+
+type Callback = func(ctx context.Context) (any, error)
+
+type Transaction interface {
+	Execute(ctx context.Context, cb Callback) (any, error)
+}