feat: introduce configurable future partition buffer and add monitoring for future partitions.

postgresql/procedures/00_partitions_init.sql

@@ -11,6 +11,7 @@ CREATE TABLE IF NOT EXISTS partitions.config (
     table_name      text NOT NULL,
     period          text NOT NULL CHECK (period IN ('day', 'week', 'month', 'year')),
     keep_history    interval NOT NULL,
+    future_partitions integer NOT NULL DEFAULT 5,
     last_updated    timestamp WITH TIME ZONE DEFAULT now(),
     PRIMARY KEY (table_name)
 );