New item announcements can potentially be skipped if a feed contains multiple items in a row with identical pub_dates

[connorkuehl]

For example, if goose is processing the following notifications:

   title   |        pub_date
-----------+------------------------
Article A  | 2023-07-26 20:50:41+00
Article B  | 2023-07-26 20:50:45+00 <-- identical
Article C  | 2023-07-26 20:50:45+00 <-- identical

And a situation like this occurs:

fetch pending notifications -> announce Article A -> announce Article B -> goose process killed/crashed -x

When goose comes back up, the SQL query for fetching the pending notifications will not include Article C because its WHERE clause has something like articles.pub_date > last_pub_date.