422 error when adding a workflow without name

[MaelAudren]

When a user wants to add a workflow to the bucket without name the returned exception is 422 unprocessable entity. It would be more relevant to have a Bad Request 400 error.
That exception is returned because the server consider that when a name is not provide, the user should provide a zip file. This ambiguity relies on the request double purpose, on one hand it handles archive on the other hand it handles workflows.
The solution would be split the current request into two requests.