Mock CTO interview: changing a response format for one B2B client with API versioning

# ======================================================================
# Q: CTO: "A large B2B customer wants a change in the response format. How do
# you do it without breaking the others?"
#
# You: "If the change is adding a field, it is not breaking and I ship it in v1.
# If it changes or removes fields, I release v2 with URL versioning. The
# business logic stays shared, only the serializer changes. On v1 I send
# Deprecation and Sunset headers, watch the logs to see who still uses it, and
# notify them before shutting it down."
# ======================================================================

class OrderViewSet(viewsets.ReadOnlyModelViewSet):
    def get_serializer_class(self):
        return OrderV2Serializer if self.request.version == 'v2' else OrderV1Serializer

    def finalize_response(self, request, response, *args, **kwargs):
        response = super().finalize_response(request, response, *args, **kwargs)
        if request.version == 'v1':
            response['Deprecation'] = 'true'
            response['Sunset'] = 'Wed, 31 Mar 2027 00:00:00 GMT'
        return response