feat: Add Waitlists API support

[aksman-dev]

Summary

Adds the waitlists REST API surface to workos.userManagement:

• listWaitlists() — GET /user_management/waitlists (single page; the endpoint is not paginated and its cursors are always null)
• getWaitlist(waitlistId) — GET /user_management/waitlists/:id (accepts the default alias for the environment's default waitlist)
• listWaitlistEntries(waitlistId, options?) — GET /user_management/waitlists/:id/entries with state / email filters and standard pagination
• createWaitlistEntry(waitlistId, payload) — POST /user_management/waitlists/:id/entries with additionalFields and sendConfirmationEmail; idempotent for duplicate emails
• approveWaitlistEntry(waitlistEntryId) — POST /user_management/waitlist_entries/:id/approve
• denyWaitlistEntry(waitlistEntryId) — POST /user_management/waitlist_entries/:id/deny
• deleteWaitlistEntry(waitlistEntryId) — DELETE /user_management/waitlist_entries/:id

Method shapes, field names, and nullability follow the published OpenAPI spec (workos/openapi-spec spec/open-api-spec.yaml as of ed12feb): WaitlistEntry with approved_at, optional additional_fields, nullable waitlist_id, and the send_confirmation_email create param. Follows the existing invitations patterns (interface + *Response pair, serializer modules, AutoPaginatable lists, path-param-first method signatures).

Test plan

• npm run typecheck, npm run lint, npm run build — clean
• npx jest src/user-management/user-management.spec.ts — 167 tests pass, including new coverage for all seven methods: URL construction, query-param serialization (state/email filters), body serialization (additional_fields, send_confirmation_email), the default waitlist alias, approve/deny state transitions, and the 422 user_already_exists error path

Fixes AUTH-6719

[linear-code]

AUTH-6719

[greptile-apps]

Greptile Summary

Adds the waitlists REST API surface to User Management.

• Introduces typed waitlist and waitlist-entry models with request and response serializers.
• Adds operations to list and retrieve waitlists and to list, create, approve, deny, and delete waitlist entries.
• Returns the non-paginated waitlist collection as a plain list, resolving the previously reported redundant-refetch behavior.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
src/user-management/user-management.ts	Adds seven waitlist operations and correctly models the non-paginated waitlist endpoint as a plain list without a refetch callback.
src/user-management/user-management.spec.ts	Covers waitlist URLs, filters, payload serialization, response deserialization, state transitions, deletion, and API errors.
src/user-management/interfaces/waitlist-entry.interface.ts	Defines the public and wire-format waitlist-entry contracts, including nullable approval and waitlist fields.
src/user-management/serializers/waitlist-entry.serializer.ts	Converts waitlist-entry wire fields to the SDK-facing camelCase model and normalizes a missing waitlist ID to null.

_{Reviews (2): Last reviewed commit: "fix: Return a plain list from listWaitli..." | Re-trigger Greptile}