v1 -> v2 MailingList table migration

[PatrickMTonne]

Context

Adds a one-time Django management command, copy_to_dynamodb, that migrates v1 MailingList records from PostgreSQL into the v2 Course Emailer's DynamoDB table so existing mailing lists continue to work after the v1 → v2 cutover. The command copies every MailingList row modified within a configurable window (default: the last 2 years).

Summary

• New command mailing_list/management/commands/copy_to_dynamodb.py with flags:
  • --table-name (required) — target DynamoDB table
  • --dry-run — skip put_item calls
  • --overwrite — replace existing items instead of skipping
  • --max-age-years N — only copy lists modified within N years (default 2; 0 disables)
  • --output-file PATH — per-list CSV audit trail
• Idempotent by default via ConditionExpression="attribute_not_exists(PK)"; existing v2 items are preserved and counted as skipped_existing
• Non-zero exit code when any errors are recorded
• Field mapping from v1 to v2:
  • access_level=members/everyone → valid_senders=all_members, active=True
  • access_level=staff → valid_senders=staff_only, active=True
  • access_level=readonly → valid_senders=all_members, active=False
  • course_settings.always_mail_staff → include_all_staff (defaults to True when no CourseSettings row exists)
  • date_created/date_modified → ISO 8601 UTC created_at/updated_at
  • section_id included only when present; subject_prefix, sis_section_id, and name are omitted (v2's own sync_with_canvas backfills them on first course access and won't clobber migrated settings)
• boto3 added as a direct dependency in pyproject.toml

Testing

1. Dry-run against the v2 dev DynamoDB table with a CSV audit trail: ENV=dev DJANGO_SETTINGS_MODULE=lti_emailer.settings.local uv run python manage.py copy_to_dynamodb --table-name <dev-table> --dry-run --output-file dry-run.csv
2. Real run against dev without --dry-run; inspect the DynamoDB table and confirm new items have correct PK/SK, active, valid_senders, include_all_staff, ISO UTC timestamps, and no subject_prefix/sis_section_id/name
3. Load a migrated course in the v2 frontend and confirm the mailing list appears with correct access-level settings.

Notes

• v1 PROD shows 16,217 modified email lists from the past two years:

  SELECT COUNT(*) FROM ml_mailing_list
  WHERE date_modified >= NOW() - INTERVAL '2 years';

[andresmauro17]

I was testing this locally using the CSV output file and the DynamoDB table.

All 31 existing records were copied correctly.

It should be fine if we can test all the records in the DB, and the code looks like it will work as expected.

Good implementation @PatrickMTonne 👍