De-aggregate subway ridership data into daily values

[idreyn]

Right now we aggregate subway ridership value into weekday means for a given week:

data-ingestion/ingestor/chalicelib/ridership/process.py

Line 47 in bd0e4ce

final = final.groupby(["year", "week", "route_or_line"])["validations"].mean().round().reset_index()

This is because we copied this code from the Covid Recovery Dash, which did this to provide a direct comparison to bus ridership data, which is only available weekly. But elsewhere, we can store and display daily subway ridership data.

We probably want to preserve the weekly aggregates, so this task will involve creating a second table to hold the daily (or weekly) ridership.