Remove Google Drive backups by Jan 31

[matthew-white]

Background: https://forum.getodk.org/t/backups-to-google-drive-from-central-will-stop-working-after-jan-31st/38895

In v1.5.3, we removed the ability to create a new backups config. By Jan 31, we plan to remove all functionality related to Google Drive backups. Note that not all backup functionality will be removed, only backups to Google Drive. We will still support direct backups, as well as backup restore.

Partial list of to-dos:

• Questions
  • Do we want to remove the GET version of /v1/backup, which will use the passphrase previously configured for Google Drive backups? I think we should remove the endpoint or at least put it on a deprecation path.
• Backend
  • Config frame
    • Remove support for backups.google and maybe also backups.main.
  • GET/DELETE /v1/config/backups
    • Especially if we remove the GET version of /v1/backup, I think we should remove these endpoints.
  • Migration
    • Delete the backups.google config and maybe also backups.main.
    • Drawing from the draft migration here, soft-delete any unused backup creation tokens and hard-delete those tokens' sessions, the initbkup role, and the tokens' assignments to the role.
  • Remove lib/bin/backup.js.
  • Remove Google things: lib/external/google.js, lib/task/google.js, test/util/google-mock.js
• Frontend
  • Remove the /system/backups route and the BackupList component.
  • Remove showsBackups from src/config.js.
• central
  • run-backup.sh
  • Remove run-backup.sh from crontab.

[matthew-white]

Closed by #375, getodk/central-frontend#684, and getodk/central-backend#748.