Add backfill alerting system for CHNG Outpatient Data

[jingjtang]

Description

Add backfill alerting system for CHNG Outpatient Data. The pipeline is compatible for the following magnitude:

• Count type: Covid outpatient count or total outpatient count
• Geo level: state level (ignore as, mp, gu) and county level (200 most populated counties)
• Backfill Variable:
  • backfill fraction (training and testing monthly, anchor_lag = 60 days)
  • change rates (training and testing daily, ref_lag = 1 / 7 days)
• Using Gamma GLM for model training
• Using generalized prediction residues for evaluation, taking weighted average of the residues considering how large the lags are
• Residues generated in testing data (most recent data) are compared with residues in training data to see whether they are surprisingly large or small
• Generalized residues for specific report dates or location-report date pairs with extremely large/small quantiles are reported

Changelog

• Add supporting code to delphi_backfill_alerting
• Add unit tests to tests

TO-DOs

• Work with Brian to test the elast alert while under review
• Communicate with Brian whether to delete the input cache folder which share the downloaded chng data with changhc indicator pipeline