Organize backend into product executable and shared Go modules

backend/shared/database/internal/transaction/transaction.go

@@ -0,0 +1,34 @@
+package transactionimp
+
+import (
+	"context"
+
+	"git.sendico.io/tech/sxchnge/shared/database/transaction"
+	"go.mongodb.org/mongo-driver/v2/mongo"
+)
+
+type MongoTransaction struct {
+	client *mongo.Client
+}
+
+func (mt *MongoTransaction) Execute(ctx context.Context, cb transaction.Callback) (any, error) {
+	// Reuse an outer customer workflow transaction when a token store joins it.
+	if transaction.ActiveMongoTransaction(ctx) {
+		return cb(ctx)
+	}
+	session, err := mt.client.StartSession()
+	if err != nil {
+		return nil, err
+	}
+	defer session.EndSession(ctx)
+
+	callback := func(c context.Context) (any, error) {
+		return cb(c)
+	}
+
+	return session.WithTransaction(ctx, callback)
+}
+
+func Create(client *mongo.Client) *MongoTransaction {
+	return &MongoTransaction{client: client}
+}