feat: Automatically send voucher when grant is confirmed

[marcoacierno]

When a user accepts a grant by setting the status to "confirmed", the system now automatically creates a voucher for the free ticket and sends an email to the grantee, similar to how it works for speakers.

Closes #4572

Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
pycon	Ready	Preview	Feb 9, 2026 6:49pm

[claude]

Automatically sends vouchers when grants are confirmed by users. The code correctly delegates to async tasks, handles existing vouchers (including co-speaker upgrades), and follows established patterns for speaker vouchers.

Issues Found

Error Handling

1. Missing exception handling in create_and_send_grant_voucher (grants/tasks.py:191). The task directly calls external APIs (Pretix via create_conference_voucher) without catching potential failures. If Pretix is unavailable or returns an error, the task will fail silently and the grantee won't receive their voucher. The speaker voucher code in schedule/tasks.py:406 has the same issue, but that doesn't justify repeating it here.

Potential Race Condition

2. The mutation send_grant_reply (api/grants/mutations.py:336) saves the grant status before triggering the voucher task. If a user rapidly submits multiple replies (or the mutation is called concurrently), the task could be queued multiple times for the same grant. While create_and_send_grant_voucher checks for existing vouchers, there's a window between the check and creation where a race condition could occur. Consider:
   • Using select_for_update() on the grant in the mutation
   • Making the task idempotent by checking grant status at task execution time
   • Using Celery task deduplication

Missing Integration with Admin Flow

3. The admin action create_grant_vouchers (grants/admin.py:298) creates vouchers but doesn't send emails. When admins bulk-create vouchers for confirmed grants, grantees won't be notified. This creates an inconsistent experience where user-confirmed grants get emails but admin-created vouchers don't. The admin action should call send_conference_voucher_email.delay() after creating vouchers.

Inconsistent Voucher Upgrade Logic

4. When upgrading a co-speaker voucher to a grant voucher (grants/tasks.py:222), the code only updates the database record but doesn't update the Pretix voucher. The Pretix voucher will still have 25% discount (co-speaker) instead of 100% free (grant). This means the grantee sees a free voucher code in their email, but when they try to use it in Pretix, they only get a 25% discount. The upgrade logic needs to call Pretix API to update the voucher's price_mode and value.

Testing Gap

5. The test test_create_and_send_grant_voucher_upgrades_co_speaker_voucher (grants/tests/test_tasks.py:74) mocks send_conference_voucher_email but doesn't verify that the Pretix voucher is updated. Without this verification, the production code bug in Conference #4 above wasn't caught.