pgsql: fix items order: Due to a misinterpretation, items where returned in wrong order when RSM was used. Pubsub vanilla `max_items` is reversing the items order to get last items, but when this attribute is not used (RSM being used or not), the items must be in chronological order. This patch fixes it, so RSM returns oldest items by defaut, and empty `<before/>` must be used to get last page (and thus most recent items). Items are always finally ordered chronologically inside the returned page (default by `update` time, but this can be modified when a specific order is requested). Reference field is also fixed to use `updated` instead of `item_id` when item are ordered by `update`.

-- we check version of the database before doing anything
-- and stop execution if not good
\set ON_ERROR_STOP
DO $$
DECLARE ver text;
BEGIN
    SELECT value INTO ver FROM metadata WHERE key='version';
    IF NOT FOUND OR ver!='7' THEN
        RAISE EXCEPTION 'This update file needs to be applied on database schema version 7, you use version %',ver;
    END IF;
END$$;
\unset ON_ERROR_STOP
-- end of version check

/* new "overwrite_policy" option */
ALTER TABLE nodes ADD COLUMN overwrite_policy text NOT NULL DEFAULT 'original_publisher'
	CHECK (overwrite_policy IN ('original_publisher', 'any_publisher'));

UPDATE metadata SET value='8' WHERE key='version';