Use-case: An existing Service Instance needs to be updated with a new heat-template for a VNF. A rolling upgrade requires that the existing VNF must not be deleted until the newer version VNF is up and running.

Updating the heat template will lead to a new model version in SDC. In order to create the new VNF (using SO-3635), the uuids for the existing service instance needs to be upgraded in AAI and SDNC. The new service model needs to support both old and new version of the VNF.

Validations should prevent upgrading a service instance to a model that does not support existing resources. Upgrade should only be allowed between service models with the same modelInvariantId.