The logic to determine what post excerpt to show for
a topic-level bookmark based on the last unread post
was complex and slow, so we decided to remove it and
always just use the first post excerpt.
This commit also fixes an issue where a couple of
instances of for_topic were missed when doing the
Bookmarkable refactors, so:
1. Clicking the topic bookmark link was not taking
the user to the last unread post
2. When replying to a topic where there was a topic
level bookmark with the auto delete preference
of "on owner reply", we were not removing the
bookmark from the UI correctly.
A test has been added for the former, the latter would
be quite time-consuming to test and not really worth
it considering it's quite an edge case UI bug.
49a70a37f1