Add Resend List Emails API for recipient-based status lookup

[gregv]

Summary

• Adds list_all_resend_emails() function that fetches all sent emails from Resend's List Emails API, builds a recipient-indexed lookup, and caches in Redis (300s TTL)
• Adds GET /api/admin/emails/resend-list?emails=a@b.com,c@d.com endpoint (auth-protected) for the frontend to query email delivery status by recipient address
• Invalidates the Resend email list cache after sending emails in send_volunteer_message() and send_email_to_address()

This removes the dependency on stored resend_id values for showing email delivery status — older emails or emails sent before tracking was added will now show status.

Test plan

• Call GET /api/admin/emails/resend-list with auth headers — verify it returns emails indexed by recipient
• Call with ?emails=test@example.com filter — verify only matching recipients returned
• Check Redis for resend:all_emails_index key — should appear after first call, expire after 5 min
• Send a new email via the admin panel, verify cache invalidation (key deleted)
• Verify the existing POST /api/admin/emails/resend-status endpoint still works unchanged

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds an admin-facing Resend “List Emails” integration to support recipient-based delivery status lookup, backed by a short-lived Redis cache and invalidated on new outbound sends.

Changes:

• Add list_all_resend_emails() to fetch/paginate Resend List Emails results, build a recipient-indexed lookup, and cache it (300s TTL).
• Add GET /api/admin/emails/resend-list?emails=... endpoint to query the recipient-indexed lookup (auth-protected).
• Invalidate the Resend email list cache after successful sends in send_volunteer_message() and send_email_to_address().

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.

File	Description
services/volunteers_service.py	Implements recipient-indexed Resend List Emails fetch + caching and invalidates cache after sends.
api/volunteers/volunteers_views.py	Adds admin GET endpoint to expose recipient-indexed Resend list results to the frontend.
requirements.txt	Updates resend dependency version to support List Emails pagination usage.

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[Copilot]

list_all_resend_emails() caps pagination at max_pages = 10 (max ~1000 emails) but the function name/description and response fields (total_fetched) suggest a complete list. This can silently truncate results for accounts with more history. Consider either paginating until has_more is false (with a configurable safety cap) or returning an explicit truncated/pages_fetched flag and documenting the limit.

[Copilot]

If a page fetch fails, the loop breaks and the function proceeds to build/cache an index from whatever was fetched so far, while still returning success: True. That can cache and serve partial/stale data for 5 minutes. Consider treating page fetch errors as success: False, or at least avoid caching when a page error occurred and include an incomplete flag in the response.

[Copilot]

The cache is only written when total_fetched > 0. If the Resend account has zero emails (or the filter returns none), this will re-hit the Resend API on every request until an email exists. Consider caching the empty index as a valid result (with the same TTL) to protect the Resend API and reduce latency.

Suggested change

	# Cache the full index with 300s TTL
	# Only cache if we actually fetched emails (avoid caching errors/empty results)
	if total_fetched > 0:
	set_cached(cache_key, {
	'emails_by_recipient': index,
	'total_fetched': total_fetched
	}, ttl=300)
	# Cache the full index with 300s TTL, including empty results
	set_cached(cache_key, {
	'emails_by_recipient': index,
	'total_fetched': total_fetched
	}, ttl=300)

[gregv]

@copilot For the frontend code, it reminds the following, please update the backend to handle this so I can accept this good idea for the frontend:

The resend-list request sends all recipient emails as a single comma-separated query string. With a large volunteer list this can exceed common URL length limits and cause 414/400 failures. Consider batching the request (e.g., chunks of N emails) or switching the endpoint/client to POST with a JSON body.

Suggested change
${process.env.NEXT_PUBLIC_API_SERVER_URL}/api/admin/emails/resend-list?emails=${encodeURIComponent(uniqueEmails.join(','))},
{
headers: {
Authorization: Bearer ${accessToken},
'X-Org-Id': orgId,
},
${process.env.NEXT_PUBLIC_API_SERVER_URL}/api/admin/emails/resend-list,
{
method: 'POST',
headers: {
Authorization: Bearer ${accessToken},
'Content-Type': 'application/json',
'X-Org-Id': orgId,
},
body: JSON.stringify({ emails: uniqueEmails }),

[Copilot]

@gregv I've opened a new pull request, #188, to work on those changes. Once the pull request is ready, I'll request review from you.

[gregv]

@copilot open a new pull request to apply changes based on the comments in this thread

[Copilot]

@gregv I've opened a new pull request, #191, to work on those changes. Once the pull request is ready, I'll request review from you.