This is a breaking change, remember key is still required to declare the data dependency. We should have a test for that. I can follow up with the test though

This is a breaking change, remember key is still required to declare the data dependency. We should have a test for that. I can follow up with the test though

__Originally posted by @zach-klippenstein in https://github.com/square/workflow-kotlin/pull/341#discussion_r595365311__