Release v1.39.1

Fix handling of mismatched datapoints against CDM (#630)

This was causing issues, because the code assumed that if there was no identity with `Id` in the datapoints request, it must be there using `ExternalId`. Now that we can use `InstanceId` instead, that was no longer correct.

I've fixed the issue, and also made it so that we throw an explicit exception if this should ever happen again.

There's an implicit ordering here. _Technically_ a caller could reference a timeseries in multiple ways in the same request, but I think it's fair to call that outside of what we want to support. None of our extractors currently do this, and I think it would fail against the timeseries API at another time.