Add TimeStamp field
It could happen that a field depends on a TimeStamp field, so the client has to manage it. For now, the default Char field is used and so the default value will be an empty string. But empty string is not a valid value for the field on the server side.
So for me, we should implement it on the client backend. I do not think we need to have a specific widget because the datetime one should work if needed.