This run_test helper sets up a convention that allows
us to give really short tracebacks for errors, and
eventually we can have more control over running
individual tests. (The latter goal has some
complications, since we often intentionally leak
setup in tests.)
If both users haven't posted in the current topic, then
as a second order sort, check which user has posted first
in the stream as a whole.
Fixes part of #5956; we still need to sort by sending in the
organization.
It appears that a regression introduced in
3f60074c33 caused undefined to be passed
as the subject to the recent_senders library much more often; this
fixing that, and makes the library handle such cases reasonably
without an exception regardless.
This was causing a huge number of "Tried to call a Dict method with an
undefined key." exceptions.
In recent_senders module, added a data structure to hold timestamps of
users' latest message in a topic. Also added a function to compare 2
users based on above timestamp. Added a function to process messages for
the data structure and a call in add_message_metadata. Also added node
tests for insertion of data into recent_senders.senders.