[ENG-11229] more fixes to migrate_osfmetrics_6to8

[aaxelb]

Ticket

ENG-11229

Purpose

(fix data-migration problems missed in #11741, oops)

Changes

• when migrating monthly usage reports, get fresh cumulative counts independently for each (stop trying to optimize by sorting and adding counts together)
• handle PublicItemUsageReport.item_type more consistently
  • in migrate, handle list of strings (as it sometimes/often is), so preprints are correctly special-cased (historical data stored separately)
  • when generating reports, keep the legacy item type (lower-cased django model name) in the es6 report
• more consistently treat osfid and osfid_v1 as synonyms
  • when scheduling tasks to migrate usage reports, dedupe
  • when getting cumulative counts for either osfid or osfid_v1, query for both
• move usage-report task scheduling (one task per item) to another background task, so the command to start the migration can finish quickly
  • reorder to handle usage reports first, so the scheduling task doesn't get buried and queue depth can be a helpful indicator of progress
• unswap --clear-es8-data --usage-reports and --clear-es8-data --usage-events

Side Effects

QE Notes

CE Notes

Documentation

[felliott]

is good!