Design an API versioning strategy

Design a versioning strategy for [API Name] that will need to evolve over time without breaking existing clients. Compare URL path versioning, request header versioning, and content negotiation, evaluating each against client ease-of-use, cache friendliness, and implementation complexity. Choose one approach, justify it, and implement it in [Language/Framework]. Define a deprecation policy specifying the sunset period, how deprecated endpoints are communicated via response headers and documentation, and a concrete migration path for existing API clients.