The vRealize Automation Extensibility Migration Guide document has been published and is now available on pubs.vmware.com
Doc outlines the changes that were introduced in the extensibility model between vRA 6.x and vRA 7.x.
It also describes the steps you must take to adapt the extensibility use cases and workflows, so that they continue working as expected after the upgrade to vRealize Automation 7.x
It comes with a bunch of sample vRO workflows embedded for easy consumption 
