chore: include test for pgbouncer schema

Author: kangmingtay

migrations/tests/database/exists.sql

@@ -1,6 +1,7 @@
 
 SELECT has_schema('public');
 SELECT has_schema('auth');
+SELECT has_schema('pgbouncer');
 SELECT has_schema('extensions');
 SELECT has_schema('graphql');
 SELECT has_schema('graphql_public');