fix: ensure that pg_stat_statements is always created as an ext

Otherwise, we will have issues with this exporter.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

services/monitoring/exporters/postgres.nix

@@ -23,6 +23,9 @@ in
     };
 
     services.postgresql.settings.shared_preload_libraries = "pg_stat_statements";
+    systemd.services.postgresql.postStart = lib.mkAfter ''
+      ${config.services.postgresql.package}/bin/psql -U postgres -c "CREATE EXTENSION IF NOT EXISTS pg_stat_statements;";
+    '';
 
     bagel.monitoring.grafana-agent.exporters.postgres.port = 9104;
   };