Ignore old RSS entries

Ignore a new entry within a followed feed depending on a condition (liberty to the implementors)

• more than 1 week old
• older than any other already seen entry from that feed
• older than any other entry in the given feed file at present
• predates adding the hookshot bot to the room
• predates to action of first subscribing to the given feed in the room

I think it worked correctly with the old RSS bot.

We're following a feed that includes the few most recent items matching a given filter (it's StackOverflow in our case). In case one of the most recent items vanish from the feed, further results appear within the top matches that can be from last year. This happens when spam got deleted or if the filter only matches open issues and one of them got solved. The RSS bot as is then sends these old entries to the room as if they were new, causing both confusion and notification fatigue for members.

• https://en.wikipedia.org/wiki/Alarm_fatigue

Start by locating the RSS feed processing and reviewing how entries are tracked for a followed feed; the issue suggests comparing the behavior with the old RSS bot. Choose and document a rule for excluding entries that predate the relevant feed or subscription history, while preserving notifications for genuinely new items and avoiding stale StackOverflow matches.