Step State
The initial state is IN_PROGRESS. The only legal state transitions are * IN_PROGRESS -> COMPLETE A PRECONDITION_FAILED will be returned if an invalid transition is requested. It is valid to create Step with a state set to COMPLETE. The state can only be set to COMPLETE once. A PRECONDITION_FAILED will be returned if the state is set to COMPLETE multiple times. - In response: always set - In create/update request: optional