feat: add configurable retention for aibridge (#20828)

Closes https://github.com/coder/internal/issues/1134

---------

Signed-off-by: Danny Kopping <danny@coder.com>

coderd/database/queries/aibridge.sql

@@ -326,3 +326,38 @@ FROM
     prompt_aggregates pa,
     tool_aggregates tool_agg
 ;
+
+-- name: DeleteOldAIBridgeRecords :one
+WITH
+  -- We don't have FK relationships between the dependent tables and aibridge_interceptions, so we can't rely on DELETE CASCADE.
+  to_delete AS (
+    SELECT id FROM aibridge_interceptions
+    WHERE started_at < @before_time::timestamp with time zone
+  ),
+  -- CTEs are executed in order.
+  tool_usages AS (
+    DELETE FROM aibridge_tool_usages
+    WHERE interception_id IN (SELECT id FROM to_delete)
+    RETURNING 1
+  ),
+  token_usages AS (
+    DELETE FROM aibridge_token_usages
+    WHERE interception_id IN (SELECT id FROM to_delete)
+    RETURNING 1
+  ),
+  user_prompts AS (
+    DELETE FROM aibridge_user_prompts
+    WHERE interception_id IN (SELECT id FROM to_delete)
+    RETURNING 1
+  ),
+  interceptions AS (
+    DELETE FROM aibridge_interceptions
+    WHERE id IN (SELECT id FROM to_delete)
+    RETURNING 1
+  )
+-- Cumulative count.
+SELECT
+  (SELECT COUNT(*) FROM tool_usages) +
+  (SELECT COUNT(*) FROM token_usages) +
+  (SELECT COUNT(*) FROM user_prompts) +
+  (SELECT COUNT(*) FROM interceptions) as total_deleted;