Optional. Used to perform a consistent read-modify-write.
This field should be left blank for a
CreateWorkflowTemplate request. It is required for an
UpdateWorkflowTemplate request, and must match the current
server version. A typical update template flow would fetch the
current template with a GetWorkflowTemplate request, which
will return the current template with the version field
filled in with the current server version. The user updates
other fields in the template, then returns it as part of the
UpdateWorkflowTemplate request.
