feat: add database-backed invitation logging and resilient bulk invitations

[mroderick]

Summary

Fixes #2542 - Adds database-backed logging for workshop invitations and makes bulk invitation creation resilient to individual failures.

This enables administrators to:

• See who initiated an invitation job and when
• Track which workshop/chapter invitations were sent for
• Monitor success/failure/skip counts in real time
• View failed invitations with detailed error reasons
• Automatically clean up logs after 180 days

Additionally, bulk invitation creation now continues gracefully if any individual member fails, rather than crashing the entire batch.

Problem

When sending workshop invitations in bulk, two problems existed:

1. No logging - There was no way to track which invitations were sent, who initiated them, or which ones failed. Debugging invitation issues required manual database queries.

2. Fragile batch processing - If any single member failed during invitation creation (e.g., due to a database constraint violation), the entire process would crash. The remaining members would never receive invitations.

For example, if sending invites to 700 members and the 300th member's invitation creation failed, the remaining 400 members would never be invited.

Solution

Invitation Logging

Added a polymorphic logging system with two models:

• InvitationLog - Tracks a batch of invitations (who initiated, when, for what workshop, success/failure counts, status)
• InvitationLogEntry - Tracks each individual invitation attempt (member, status, failure reason, processed_at)

The InvitationLogger service integrates with InvitationManager to log every workshop/virtual workshop email send. Logs are viewable from the admin workshop page.

Resilient Bulk Invitations

• Use find_or_create_by to handle duplicate invitations safely
• Wrap invitation creation in begin/rescue to catch StandardError
• Log errors with context (workshop_id, member_id) but NO PII
• Continue processing remaining members after individual failures

Changes

Commit	Description
5db15526	Migration, models (InvitationLog, InvitationLogEntry), fabricators, model specs
9312a829	InvitationLogger service with batch tracking, service specs
c3bbc8d9	Integration into InvitationManager, Workshop association, controller params, integration specs
234fca52	Admin UI (controller, policy, views, routes, seeds), controller & policy specs
189a0ba4	Cleanup job (180-day retention), rake task, job specs

Total: 42 tests passing across all commits

How to Verify

Set up an admin user

# In rails console:
bundle exec rails console

# Make yourself admin:
Member.find_by(email: "your@example.com").add_role(:admin)

View invitation logs

1. Start the server: bundle exec rails server
2. Navigate to any workshop: /admin/workshops/:id
3. You should see an "Invitation Logs" section with recent logs
4. Click "View All Logs" to see the full list
5. Click any log to see detailed entries (success/failure/skip per member)

Seed data

bundle exec rake db:seed

This creates sample invitation logs across past workshops.

Cleanup expired logs

bundle exec rake invitation_logs:cleanup

Run tests

bundle exec rspec spec/models/invitation_log_spec.rb \
  spec/models/invitation_log_entry_spec.rb \
  spec/services/invitation_logger_spec.rb \
  spec/models/invitation_manager_logging_spec.rb \
  spec/controllers/admin/workshop_invitation_logs_controller_spec.rb \
  spec/policies/invitation_log_policy_spec.rb \
  spec/jobs/cleanup_expired_invitation_logs_job_spec.rb

All 42 tests pass.

[mroderick]

Putting this back to draft, I have more improvements up my sleeve