Make provenance in seasonal snapshots consistent with forecast and real-time

[getorymckeag]

The provenance section of the seasonal snapshot is not consistent with the forecast and real-time snapshot. This creates confusion.

[getorymckeag]

We have also considered the way that seasonal ratings get into the clearinghouse. For example, they could come through proposals, OR could be modeled, as is traditional practice for many systems.

One could, for debugging purposes, which path the seasonal ratings took to get into the clearinghouse. During the monthly steerco meeting, we decided this is NOT an interop usecase we are currently interested in.