Assume the role of a Lead Software Engineer. You are tasked with refactoring a 10-year-old monolithic Java application into a microservices architecture. The monolith contains spaghetti code, circular dependencies, and lacks test coverage. Outline a step-by-step migration strategy that includes the Strangler Fig pattern. Identify how you would extract bounded contexts, manage data integrity during the transition, handle authentication/authorization across services, and ensure zero downtime deployment. Discuss potential pitfalls and rollback strategies.