Fix #12880 : notifications stop to work if last read event has been purged in a room

[laurent-treeb]

Fix #12880 : notifications stop to work if last read event has been purged in a room

Following this comment #12880 (comment) that explains where the bug is, i choose a third way to resolve by updating the "The second query gets all event_push_actions for rooms with no read receipts." by adding rooms that have a read receipt that pointing to purged event.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Pull request includes a sign off
• Code style is correct
  (run the linters)

[DMRobertson]

This has a merge conflict. Can you resolve it?

[clokep]

Also -- please update the title and description with a bit of information of what this PR accomplishes and how it does it.

[laurent-treeb]

This has a merge conflict. Can you resolve it?

Sorry no. A big merge has been done in 1.62 with this merge : #13005

So the PR may be helpfull for someone who wants to override a Synapse server before the 1.62. (I change the destination branch of the PR).

[clokep]

Closing as the author has stated they are not interested in continuing to work on this PR.