feat(alerts): V17 migration — drop ACKNOWLEDGED, add read_at + deleted_at

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/main/resources/db/migration/V17__alerts_drop_acknowledged.sql

@@ -0,0 +1,53 @@
+-- V17 — Alerts: drop ACKNOWLEDGED state, add read_at/deleted_at, drop alert_reads,
+-- rework open-rule unique index predicate to survive ack (acked no longer "closed").
+
+-- 1. Coerce ACKNOWLEDGED rows → FIRING (acked_at already set on these rows)
+UPDATE alert_instances SET state = 'FIRING' WHERE state = 'ACKNOWLEDGED';
+
+-- 2. Swap alert_state_enum to remove ACKNOWLEDGED (Postgres can't drop enum values in place)
+--    First drop all indexes that reference alert_state_enum so ALTER COLUMN can proceed.
+DROP INDEX IF EXISTS alert_instances_open_rule_uq;
+DROP INDEX IF EXISTS alert_instances_inbox_idx;
+DROP INDEX IF EXISTS alert_instances_open_rule_idx;
+DROP INDEX IF EXISTS alert_instances_resolved_idx;
+
+CREATE TYPE alert_state_enum_v2 AS ENUM ('PENDING','FIRING','RESOLVED');
+ALTER TABLE alert_instances
+  ALTER COLUMN state TYPE alert_state_enum_v2
+  USING state::text::alert_state_enum_v2;
+DROP TYPE alert_state_enum;
+ALTER TYPE alert_state_enum_v2 RENAME TO alert_state_enum;
+
+-- Recreate the non-unique indexes that were dropped above
+CREATE INDEX alert_instances_inbox_idx     ON alert_instances (environment_id, state, fired_at DESC);
+CREATE INDEX alert_instances_open_rule_idx ON alert_instances (rule_id, state) WHERE rule_id IS NOT NULL;
+CREATE INDEX alert_instances_resolved_idx  ON alert_instances (resolved_at) WHERE state = 'RESOLVED';
+
+-- 3. New orthogonal flag columns
+ALTER TABLE alert_instances
+  ADD COLUMN read_at    timestamptz NULL,
+  ADD COLUMN deleted_at timestamptz NULL;
+
+CREATE INDEX alert_instances_unread_idx
+  ON alert_instances (environment_id, read_at)
+  WHERE read_at IS NULL AND deleted_at IS NULL;
+
+CREATE INDEX alert_instances_deleted_idx
+  ON alert_instances (deleted_at)
+  WHERE deleted_at IS NOT NULL;
+
+-- 4. Rework the V13/V15/V16 open-rule uniqueness index:
+--    - drop ACKNOWLEDGED from the predicate (ack no longer "closes")
+--    - add "AND deleted_at IS NULL" so a soft-deleted row frees the slot
+DROP INDEX IF EXISTS alert_instances_open_rule_uq;
+CREATE UNIQUE INDEX alert_instances_open_rule_uq
+  ON alert_instances (rule_id, (COALESCE(
+        context->>'_subjectFingerprint',
+        context->'exchange'->>'id',
+        '')))
+  WHERE rule_id IS NOT NULL
+    AND state IN ('PENDING','FIRING')
+    AND deleted_at IS NULL;
+
+-- 5. Drop the per-user reads table — read is now global on alert_instances.read_at
+DROP TABLE alert_reads;