fix(slack): Normalize email casing in linkExistingSlackMembers

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Detail bug report: View on Detail

Bug

linkExistingSlackMembers (the hourly Slack-sync cron fallback) matched apply-time DB emails against Slack's users.list profile.email using JavaScript's case-sensitive in operator on an un-normalized lookup, and its previousParticipants Prisma-in copy was similarly case-sensitive. Any student/mentor whose apply-time email casing differs from the casing Slack holds (e.g. DB First.Last@Company.com vs Slack first.last@company.com) was silently never matched, leaving slackId null indefinitely — so downstream consumers that filter on slackId treated the user as absent from the workspace. This was inconsistent with every other cross-system email join in the codebase (postmark.ts, Attio sync), which normalize casing.

Fix

• Added normalizeEmail(email) = email.toLowerCase().trim() and applied it to both sides of every comparison in src/slack/linkExistingSlackMembers.ts: the searchStudents/searchMentors lookup keys, the users.list member filter and row-id lookup, and the previousParticipants in-memory match/lookup/delete.
• The previousParticipants Prisma findMany now passes email: { in: [...], mode: 'insensitive' } so prior-event rows with differing casing are found on a default case-sensitive Postgres collation.
• Added an optional deps?: { prisma?, slack? } injection seam to linkExistingSlackMembers (defaults to Container.get(PrismaClient) + getSlackClientForEvent(event)), so the cron path is unit-testable without a live DB / Slack workspace. The sole runtime caller (slackSync.ts) is unchanged and backward-compatible.

mode: 'insensitive' is supported by the installed Prisma client's StringFilter and was verified against a real Postgres 14 instance (default en_US.utf8 collation).

Testing

• Added tests/testLinkExistingSlackMembers.ts (5 node:test cases): normalizeEmail lowercase+trim, student case-mismatch linking (the reported bug), mentor case-mismatch linking, whitespace-divergent linking (guards the .trim() half), and the previousParticipants case-insensitive copy — which also asserts the Prisma query carries mode: 'insensitive' and that the prior copy removes the row from the search set before users.list runs.
• Offline unit tests, the existing tests/testSlackReporting.ts, npx tsc --skipLibCheck --noEmit, and npm run build all pass. (No lint is available — the repo's pinned @typescript-eslint parser fails under the installed typescript@5.2.2, independently of this change.)
• End-to-end verification against a real Postgres 14 container: applied the Labs schema via prisma db push (the migration chain hits a pre-existing ordering quirk on fresh DBs), seeded an event/project plus case-mismatched, exact-case, whitespace-divergent, and already-linked rows, then drove the real fixed function against the live DB with a mock users.list returning lowercased casings. All affected rows acquired the expected slackId; the already-linked row was untouched. A data-layer join demonstration confirmed the case-sensitive join (the bug) matches 1/4 of the seeded null rows while the case-insensitive join (the fix) matches 4/4.
• The real-Slack users.list capture could not be run: no Slack token is available in this environment (env | grep -iE SLACK is empty; no .env), so the run would be rejected by Slack. It was substituted with a mock users.list payload modeling the lowercased profile.email casings Slack returns; the Postgres half was fully exercised.

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