[Cloud function]: Daily sync of research meta-data

[benfurber]

Due to the move to discussion documents holding the comments for each research update and changing comments from being deleted from the DB to be updated to _deleted, it's much more common and noticiable that the comment count stored for each research articles (totalCommentCount) gets out of sync with the reality.

Solution: Accept that certain changes in data will be fallible and have a cloud function that runs daily for research that:

1. Identifies all the currently not _deleted and published research articles.
2. Identifies all the published and not _deleted updates for each article.
3. Identifies discussion document for each research update (found through the _id of an update being the sourceId of the discussion).
4. Count the not _deleted comments for the discussion.

That should then give a total that can be set as the totalCommentCount for the research.