Setting date_time in Quiver.create_element produce wrong results

[guilhermebodin]

In an internal model setting a structure like this one

            Quiver.create_element!(db, "XXXX";
                label = label,
                date_time = string.(ts.dates),
                observation = ts.values,
            )

produces so that the date_time of all time series groups in the collection be populated with ts.dates. In my opinion this should not be passed to all time series groups.
To set the dates of time series groups the API that should be used is only Quiver.update_time_series_group!