If the user talk edit or mention coincides with exactly one new comment:
* Change the primary link to be a direct link to the comment
* Add a text snippet to notifications that don't already include one
(user talk edits that are not new sections).
This is done for all such notifications, regardless of whether anyone
has topic subscriptions enabled.
Bug: T281590
Bug: T253082
Change-Id: I98fbca8e57845cd7c82ad533c393db953e4e5643
Adding test cases in a separate commit to make it easier to review how
the test results change after I98fbca8e.
* For mentions, the 'mentioned-users' extra parameter is copied to our
event (which is then used to avoid duplicate notifications).
* For user talk page edit, nothing special happens right now (we use
the target page title to avoid duplicate notifications, but this is
not apparent from the test case, since page titles are not present).
Bug: T281590
Bug: T253082
Change-Id: I153e7735f63f1e2643ed881281d807313cd699c3