-- Nachklang e.V. Calendar module — step 1 of docs/calendar-auth-migration.md.
-- Adds the bridging columns that let an event record who created it as an
-- *admin* user id (VARCHAR(36)) alongside the legacy calendar users.user_id
-- (INT). Apply manually against the CALENDAR_DB database:
--   mysql -h <DB_HOST> -u <DB_USER> -p <CALENDAR_DB> < 001_add_admin_user_bridge.sql
--
-- Numbered 001 because this is the first migration this repo owns for the
-- calendar schema: the tables themselves predate it and were provided by the
-- repo owner (mirrored for dev in docker/init/01-calendar-schema-dev.sql).
--
-- Nothing reads these columns yet — step 3 introduces the dual-read. Adding
-- them first means the backfill in step 2 has somewhere to write, and this
-- migration can be applied to production on its own without any code change.
--
-- No foreign key, on purpose. The admin `user` table lives in a *different*
-- database (nachklang_admin) behind a different connection pool, and a
-- cross-schema FK would tie the two schemas' lifecycles together: you could no
-- longer dump, restore or move one without the other. The reference is
-- enforced in application code, which is also where the legacy/new fallback
-- lives.
--
-- The collation is pinned to the admin database's (utf8mb4_unicode_ci) rather
-- than inherited from the calendar tables' utf8mb4_general_ci. These columns
-- hold ids that only ever compare against nachklang_admin.user.id, and a
-- mismatched collation makes any such comparison fail at runtime with
-- "Illegal mix of collations" instead of at review time.

ALTER TABLE `events`
    ADD COLUMN `created_by_user_id` VARCHAR(36)
        CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci
        NULL DEFAULT NULL AFTER `created_by_id`,
    ADD KEY `events_created_by_user_idx` (`created_by_user_id`);

ALTER TABLE `event_versions`
    ADD COLUMN `version_created_by_user_id` VARCHAR(36)
        CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci
        NULL DEFAULT NULL AFTER `version_created_by_id`,
    ADD KEY `event_versions_created_by_user_idx` (`version_created_by_user_id`);